OTDR: Product-Specific Questions
M200:
Q: How do I convert my M200 test results into a PDF document?
A: You need to use the Test Result Manager (TRM®) PC software. You can use either TRM® 2.0 (paid version) or TRM® v1.6.5 (free version).
M210:
Q: Can I save traces for viewing later?
A: Yes. There is a dedicated Save key. In the Main Menu “File” tab, set up the location/folder (Internal or USB) to save the file, the file naming format, and fiber number. The fiber number will automatically increment after each trace is saved.
Q: What is the advantage of the Expert Auto mode?
A: User is able to select a single and have the OTDR set the other test parameters.
Q: What is the advantage of the Expert Auto Once mode?
A: User is able to select one or more wavelengths, let the OTDR select Pulse Width, Time, and Range for one test. Then allow the user to adjust any of these test parameters for the next test(s).
Q: What is the purpose of the Real-Time mode?
A: With a launch cable, the Real-Time mode may be used to quickly view many short fiber links. It can also be used to quickly “trace” short fiber links.
Q: Why do I need to use a launch and receive cable?
A: A launch cable allows the OTDR to settle down after the initial pulse and provides a reference cable for testing the first connector on the fiber under test. A receive cable provides a reference cable for testing the last connector of the fiber under test.
M310/M210e:
Q: Can I save traces for viewing later?
A: Yes. There is a dedicated Save key. In the Main Menu “File tab”, set up the location/folder (Internal or USB) to save the file, the file naming format, and fiber number. The fiber number will automatically increment after each trace is saved.
Q: What is the advantage of the Expert Auto mode?
A: User is able to select a single and have the OTDR set the other test parameters.
Q: What is the advantage of the Expert Auto Once mode?
A: User is able to select one or more wavelengths, let the OTDR select Pulse Width, Time, and Range for one test. Then allow the user to adjust any of these test parameters for the next test(s).
Q: What is the purpose of the Real-Time mode?
A: With a launch cable, the Real-Time mode may be used to quickly view many short fiber links. It can also be used to quickly “trace” short fiber links.
Q: Why do I need to use a launch and receive cable?
A: A launch cable allows the OTDR to settle down after the initial pulse and provides a reference cable for testing the first connector on the fiber under test. A receive cable provides a reference cable for testing the last connector of the fiber under test.
Q: Why should I average OTDR results from both ends (bi-directional averaging)?
A: In networks built with a mix of fiber types (older and newer fiber, G.652 and G.655 or G.657 fiber), an OTDR scan may show excess loss at a splice joining these fibers when viewed in one direction, and may show “gain” (negative loss) when viewed in the opposite direction. The actual splice loss can be computed by averaging the excess loss in one direction with the gain in the opposite direction. If the average loss meets the carrier’s splice acceptance criteria, there is no need to re-splice the connection, even though the excess loss when viewed in one direction exceeds the splice acceptance criteria. Bi-directional averaging automatically pairs traces taken from both ends, averages them and presents the averaged results.
Q: To perform bi-directional averaging, must both traces be obtained using the same OTDR?
A: Two different M310s may be used to acquire the results, but the results from both ends must be available in one M310 for that M310 to perform bi-directional averaging. This is most easily accomplished if the same M310 is used to test from both ends.
Q: How should files be named so the M310 can automatically match results from both ends and perform bi-directional averaging?
A: There is no special naming convention required for automatically matching results from both ends. What is required is that the both tests are run, and results stored, in the same job\route\cable\ file. It’s preferable to run, and save, tests from both ends in the same fiber file, and use the same OTDR, for better results organization. After running the test with the OTDR at one end (say END1) the user must change the “OTDR Located At” in the Job Settings screen to the other end (END2 in this case) when running the test in the other direction. Bi-directional Analysis must be set to “ON” in the Events Setting Screen.
Q: Must the same OTDR settings be used from each end to perform bi-directional averaging?
A: Yes. The OTDR must be set to the same range and pulse width settings for both traces in order to average the results.
Q: If I use a launch fiber when testing from one end, must I also use a launch fiber of the same length when testing from the other end?
A: It is recommended that the same launch cable be used in both directions to ensure the greatest accuracy in the average Link Loss calculation. While in theory different launch cables (either of the same or different length) could be used in each direction the bi-directional averaging of Link Loss may be skewed by differences in connector losses between cables.
Q: If I use a receive fiber when testing from A -> B, must I also use a receive fiber of the same length when testing B -> A?
A: It is recommended that the same receive cable be used in both directions to ensure the greatest accuracy in the average Link Loss calculation. While in theory different receive cables (either of the same or different length) could be used in each direction the bi-directional averaging of Link Loss may be skewed by differences in connector losses between cables.
Q: If an event is detected in A -> B direction, but not in the B ->A direction, can results still be averaged? If so, how is the average loss computed for the event detected in one direction but missed in the other direction?
A: The “missing event” is added as a 0 dB loss event. The average loss is ½ the measured loss of the automatically detected event (Avg. = (measured + added 0 dB) / 2)
Q: If the fiber in A -> B direction was measured at a significantly different length than in the B -> A direction, can the traces be averaged?
A: No. If length in the second test direction is significantly different than the length measured in the first test direction then a screen will pop up indicating that the unit is unable to perform bi-directional analysis due the mismatch in link lengths.
Q: Why is macrobend detection only available in the QUAD and 1310/1550 nm single-mode M310s?
A: Microbends and macrobends result in excess loss in single-mode fibers at longer wavelengths. Consequently, microbend and macrobend detection is only available by comparing single-mode traces obtained at 1310 and 1550 nm.
Q: What are the criteria used by the M310 to detect a micro- or macrobend?
A: A micro- or macrobend event is detected when the loss of a point defect at 1550 nm exceeds the loss at 1310 nm by 0.2 dB or more.
Q: If a loss event is detected at 1550 but not 1310 nm, can a micro or macrobend still be detected?
A: Yes. In this case, the M310 will add a 0 dB loss event at 1310 and report the new event as a macrobend, assuming the loss at 1550 nm is ≥0.2 dB.
Q: How is a micro- or macrobend reported?
A: Micro/macrobends are indicated in the event table with an event type displayed as ![]()
C840:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: When using my C840s are connected together to perform AT, the units won’t link, why?
A: In order for the C-840 and C-850 units to link properly, both must be set to the same fiber type (MM or SM). One unit must be set on “Main” while the other unit is set for “Remote”. After properly cleaning all patch cords, they must be connected between the correct OLS port (MM or SM) of the Main unit to the OPM port of the Remote and the second jumper must connect between the correct OLS port (MM or SM) of the Remote back to the OPM port of the Main unit. In most cases, the C-850 is selected as the Main unit to store all test results. This allows the larger C-850 unit to stay stationary at the MDF, while the smaller C-840 is transported in the field to each IDF.
C850:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: When my C850s are connected together to perform AT, the units won’t link, why?
A: In order for the C-840 and C-850 unfdg to link properly, both must be set to the same fiber type (MM or SM). One unit must be set on “Main” while the other unit is set for “Remote”. After properly cleaning all patch cords, they must be connected between the correct OLS port (MM or SM) of the Main unit to the OPM port of the Remote and the second jumper must connect between the correct OLS port (MM or SM) of the Remote back to the OPM port of the Main unit. In most cases, the C-850 is selected as the Main unit to store all test results. This allows the larger C-850 unit to stay stationary at the MDF, while the smaller C-840 is transported in the field to each IDF.
Q: What OTDR have TIA standard certification and troubleshooting capabilities?
A: The C-860 QUAD OTDR and Certification Test Kit is the best choice.
C880:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: While testing angled SC connectors on my network, I keep getting bad results on my C880 kit.
A: Make sure you have not plugged angled SC plugs into the OLS port. When setting the reference and testing, pay careful attention to placing the ASC connectors only into the OPM port, not the OLS port, and your reference and test results work out OK. This will require using a hybrid UPC to APC launch jumper for each OLS port when testing angled connectors on your network.
Fiber Ring:
Q: Why do I need to use fiber rings?
A: Fiber rings allow the technician to measure the front panel and rear panel insertion loss and return-loss of the network under test. This will allow the technician to create a final report in TRM® that will show total Link Loss and Link ORL values.
Q: Why can’t I just use the launch cable and test the network from both directions?
A: Testing the network in both directions will confirm that the network may operate as designed, but will not allow TRM® to properly report Link Loss and Link ORL.
Q: How do I know which size fiber rings to use for my test?
A: The fiber rings must be longer than the length of the pulse of light by at least 1.5 times. This allows for the recovery of the attenuation dead-zone caused by the initial reflective spike located at the OTDR test port. The final patch panel also causes a reflective spike, which is why a receive cable must be used as well.
The length of the pulse of light may be calculated by dividing the PW in ns (nanoseconds) by 10. This will provide the approximate length of the pulse of light in meters.
Examples
- 100ns/10 = 10-meter light pulse. The standard 150-meter fiber rings will be adequate to test any fiber network at 100ns. The maximum PW that can be used with a 150-meter fiber ring is 1,000ns or 1.0µS.
- 1,000ns /10 = 100-meter light pulse. The 150-meter fiber ring is exactly 1.5 times the length of the pulse of light traveling down the fiber.
Refer to chart below for additional fiber ring and fiber box lengths:
Flex Tester:
Q: How do you setup the unit to tell it you have 2 or 3 splitters?
A: To test through multiple splitters, multiply together the split ratios and set the PON Split Ratio to that value. For example, if you have 1X8 followed by 1X8, set PON Split Ratio to 1X64. If you have 1X4 plus 1X8, set PON Split Ratio to 1X32. If you add 1X2 to this to create 1X2 + 1X4 + 1X8, set PON Split Ratio to 1X64.
Q: Is the Range value that you put in the range from the CO to the first splitter?
A: When Test = Through Splitter, the Range should be set to slightly exceed the distance from ONT (at customer premise) to OLT (at central office/local exchange). We usually recommend 25-30% longer than the network length. Max PON length is 20 km. Available Range selections are: 250 m, 500 m, 1000 m, 1.5 km, 3 km, 6 km, 15 km, 30 km. FLX380/OFL280 will automatically select pulse width and resolution settings based on the Range and PON Split Ratio. The table below shows the Pulse/Resolution settings for FLX380.
You can see that as longer range or higher split ratio is selected, wider pulse or Normal resolution is selected to achieve greater dynamic range needed to test through higher split ratios or longer networks. If a user is not happy with the results they get using the selected Range & PON Split Ratio, they can adjust the Range or PON Split Ratio setting to force a wider pulse width (for a less noisy trace) or a narrower pulse width (to see closely spaced events more clearly before the splitter(s)).
Q: If shooting from the customer ONT, is the Range the distance from ONT/ONU to the splitter?
A: If you only wish to test from the ONT to the splitter (not through the splitter), you can either use PON OTDR with Test = Customer Fiber Only, or you can use Full Auto (Point-to-Point).
Q: When purchasing a FlexTester, should I order UPC or APC ports?
A: To determine if an OTDR should have UPC or APC test ports, it is helpful to know if most of the networks to be tested will be UPC or APC. Since an OTDR is almost always used with a launch cable, it is the launch cable that does any necessary conversion from one connector style to another. Having the test port match the network connector style, UPC or APC, simply means the technician will need fewer different types of launch cables, but it does not preclude testing all types of network connections. For example, an FLX380 with an APC test port would require launch cables with at least one APC connector to be directly attached to the OTDR port. The other end of the launch cable can be either UPC or APC, depending on the network to be tested. If most of the networks are APC, then most of the launch cables would be APC on both ends, allowing them to have two connector types, such as SC/APC and LC/APC. This would allow testing of both SC and LC networks, simply by swapping ends of the launch cable and changing the OTDR adapter cap. Note that it is not the adapter cap that determines if a port is APC or UPC; it is the ferrule inside the unit. This means the OTDR is manufactured with either an APC or UPC ferrule. All OTDR adapter caps fit both styles. If the FLX380 is UPC, then the opposite would apply regarding the launch cables to be used.
Q: Does the Flex Tester test for Optical Return Loss?
A: The FLX380 does test for ORL. If launch and receive cables are used, ORL measurement excludes contributions from the launch and receive cables, as well as any excess reflection from the open end of the far-end receive cable.
Q: In the three wavelength models, if a fiber is shot in all three wavelengths, are the traces saved as one file or three different files?
A: Tri-wavelength test results are saved in three separate .SOR files, all having the same prefix.
Q: Can the traces be saved directly to an external flash drive or do they have to be saved on the OTDR then transferred to a computer later?
A: FlexTester results cannot be saved to an external flash drive, so they do have to be stored internally then transferred to computer later.
Q: How do I enable or disable the Launch Quality Check?
A: Launch Quality Check may be enabled/disabled from the Settings menu (accessible by pressing right tab key (→) when the Main Menu is displayed).
Q: What are the criteria for determining poor launch quality?
A: Poor launch quality is detected if loss at the OTDR connector exceeds approximately 0.9 dB, or the reflectance at the OTDR connector exceeds approximately -40 dB.
Q: What are the possible causes for poor launch quality?
A: Poor launch quality is likely due to one of the following problems:
- Dirty or damaged connector on the OTDR or mating connector on the launch cable or jumper attached to the OTDR;
- Mismatched connector types; e.g. OTDR is built with UPC connector, but is mated to an APC connector on the attached launch cable or jumper (or vice versa);
- OTDR connector adapter is loose, creating an air gap between the OTDR connector and the attached launch cable or jumper.
Q: What should I do if poor launch quality is reported?
A: Perform the following steps:
- Inspect and clean both the OTDR connector and the launch cable or jumper connector.
- If a short jumper was used, also inspect and clean the connection between the jumper and the network under test.
- Verify OTDR and launch cable or jumper both have the same connector type (UPC or APC).
- Verify the OTDR connector adapter is tight (turn clockwise to tighten).
- Press the “Re-check” softkey to repeat the launch quality check. If launch quality is now OK, OTDR test will initiate.
Q: What should I do if I’ve inspected and cleaned the connectors, verified connectors are both of the same type (UPC or APC), and verified the OTDR connector adapter is tightened, but poor launch quality is still reported after re-checking?
A: It is possible that connection quality at the OTDR is marginal (e.g. loss slightly greater than 0.9 dB or reflectance slightly higher than -40 dB), either due to wear-and-tear on connectors, or because the combined loss or reflectance of a short jumper with mated connections at both ends exceeds the launch quality loss or reflectance threshold. In this case, you may override the launch quality check and continue testing by pressing the Test key. However, you should review OTDR trace to ensure excess reflection (large reflective peak with long recovery tail) or excess loss at the OTDR connection is not producing poor test results.
Q: Can I continue an OTDR test even if poor launch quality is reported?
A: Yes, you can continue an OTDR test by pressing the Test key. This is not recommended unless you’ve already cleaned both the OTDR and launch cable connections, verified no connector mismatches, and verified OTDR connector adapter is tight.
Q: Can I obtain good OTDR results if I continue a test when poor launch quality is reported?
A: You can obtain good OTDR test results If launch quality is marginal (e.g. loss at front panel is slightly greater than 0.9 dB or reflectance is slightly greater than -40 dB). However, if excess reflection and/or loss occurs at the OTDR connector (e.g. due to dirt, damage, or an air gap), you likely will not obtain good OTDR test results.
Q: How do I enable/disable automatic macrobend detection?
A: From the OTDR Test screen, press the tab key (ï or ð) to select Events tab. Scroll down to highlight Macro-bend detection setting and press the left or right arrow key (| or }) to enable or disable macro-bend detection.
Note: Macro-bends can only be detected when OTDR test uses two or three wavelengths, such as 1310/1550 or 1310/1550/1625.
Q: Why must I test using at least two wavelengths to detect macro-bends?
A: Loss due to macro-bends is higher at longer wavelengths. Macro-bends are detected by comparing loss of a non-reflective event at a short wavelength (such as 1310 nm) to the loss at a longer wavelength (such as 1550 or 1625 nm). If the loss at longer wavelength is appreciably higher than the loss at the short wavelength, the event is identified as a macro-bend.
Q: Why does the OTDR sometimes detect and report a macrobend at 1550 nm, but reports no event at the same location at 1310 nm?
A: Often, the loss at 1310 nm due to a macro-bend will not exceed the event detection threshold, while the loss at 1550 nm does exceed the event detection threshold. In this case, the event will be reported in the 1550 nm results, but not the 1310 nm results.
Q: Why does the OTDR occasionally report a macrobend at 1550 nm, but reports the same event as the end of fiber at 1625 or 1650 nm?
A: Since bending loss is higher at longer wavelengths, it is possible for the loss due to a macro-bend to exceed the end detection loss threshold at 1625 or 1650 nm, while not exceeding the end detection threshold at 1550 nm. In this case, the event may be reported as a macro-bend at 1550 but as the end of fiber at 1625 or 1650 nm.
Q: Why am I getting an indication of Poor launch condition, even though the ferrules look good on inspection?
A: The FlexTesters will report poor launch quality if one or both of the following conditions is met:
- Loss at OTDR exceeds 0.9 dB
- Reflectance at OTDR exceeds -40 dBQ:
Q: I noticed the dead zone for this OTDR is 0.8m. How we determine this value?
A: Event dead zone is defined as, “Typical distance between the two points 1.5 dB down each side of a reflective spike caused by a -45 dB reflective event using 5 ns pulse width.” In practice, this means that two clean, mated PC connections 0.8 m apart can be visually detected in the trace since there would be a ‘valley’ between the peaks due to each reflective connection. All OTDR manufacturers use this (or a similar) definition of event dead zone. All OTDRs only meet their dead zone specs when their narrowest pulse is used. It is rare for an OTDR’s fault location algorithms to automatically detect two events this close together.
Q: Many PCs (mine included) often seem to want to install a new driver when I connect FLX380 or OFL280. When this occurs, it often takes 2-4 minutes for driver to install before PC recognizes FLX380 or OFL280. The solution is to wait for driver to install. How can I get my PC to retain the drivers?
A: While newer OFL280 and FLX380 units are shipped with a different USB chip which has improved speed and operation of USB interface, we still have the issue of PCs re-installing driver when FLX380 or OFL280 plugged in. We cannot control this (it is a PC issue). So users must simply wait for driver to be installed or recognized.
OFL250/OFL 280 Tester:
Q: Does the OFL test for Optical Return Loss?
A: While the OFL250 does not test for ORL, the OFL280 does test for ORL. If launch and receive cables are used, ORL measurement excludes contributions from the launch and receive cables, as well as any excess reflection from the open end of the far-end receive cable.
Q: In the three wavelength models, if a fiber is shot in all three wavelengths, are the traces saved as one file or three different files?
A: Tri-wavelength trace is saved as three separate .SOR files with the same prefix.
Q: Can the traces be saved directly to an external flash drive or do they have to be saved on the OTDR then transferred to a computer later?
A: FLX/OFL traces cannot be saved to an external flash drive, so they do have to be stored internally then transferred to computer later.
Q: How many traces can be saved in the OFL280 memory?
A: Formatted storage drive = 3.78GB in FAT 32, Optic version = 96KB, Software = 1.31MB, Each trace = 60KB in size, so potential storage capacity if 100% of the space could be used is > 63,000 traces.
Q: Is there any option to add more memory?
A: There is no option to add memory, but over 60,000 traces should be enough, even if they are all tri-wavelength.
Q: In the OFL280, why is the lowest splitter count in Auto Mode 1 x 8?
A: In FTTx - PON Construction test mode, the minimum split ration may be 1 x 8, but it will detect all splitters up to and including 1 x 8. So even if the splitter was a smaller 1 x 4 value, the 1 x 8 setting would be the appropriate setting to detect that splitter. The same would hold true if I set the ratio to 1 x 16 to detect a 1 x 8 splitter, it would work fine.
Q: How long will the VFL on the OFL280 stay transmitting?
A: It depends on the OFL280; earlier models turned off the VFL in about 10 minutes. An upgrade to v1.2.02 eliminated the VFL auto-off capability.
Q: What wavelengths does the OFL Light Source (OLS) provide?
A: The OFL280-102 offers 1310/1490/1550 source operation. The OFL280-103 only offers 1310/1550, while FLX380-303 and FLX380-304 offer 1310/1550/1625 nm source operation, respectively. This was to maintain consistency with past OFL280-103 operation.OTDR: Product-Specific Questions
M200:
Q: How do I convert my M200 test results into a PDF document?
A: You need to use the Test Result Manager (TRM®) PC software. You can use either TRM® 2.0 (paid version) or TRM® v1.6.5 (free version).
M210:
Q: Can I save traces for viewing later?
A: Yes. There is a dedicated Save key. In the Main Menu “File” tab, set up the location/folder (Internal or USB) to save the file, the file naming format, and fiber number. The fiber number will automatically increment after each trace is saved.
Q: What is the advantage of the Expert Auto mode?
A: User is able to select a single and have the OTDR set the other test parameters.
Q: What is the advantage of the Expert Auto Once mode?
A: User is able to select one or more wavelengths, let the OTDR select Pulse Width, Time, and Range for one test. Then allow the user to adjust any of these test parameters for the next test(s).
Q: What is the purpose of the Real-Time mode?
A: With a launch cable, the Real-Time mode may be used to quickly view many short fiber links. It can also be used to quickly “trace” short fiber links.
Q: Why do I need to use a launch and receive cable?
A: A launch cable allows the OTDR to settle down after the initial pulse and provides a reference cable for testing the first connector on the fiber under test. A receive cable provides a reference cable for testing the last connector of the fiber under test.
M310/M210e:
Q: Can I save traces for viewing later?
A: Yes. There is a dedicated Save key. In the Main Menu “File tab”, set up the location/folder (Internal or USB) to save the file, the file naming format, and fiber number. The fiber number will automatically increment after each trace is saved.
Q: What is the advantage of the Expert Auto mode?
A: User is able to select a single and have the OTDR set the other test parameters.
Q: What is the advantage of the Expert Auto Once mode?
A: User is able to select one or more wavelengths, let the OTDR select Pulse Width, Time, and Range for one test. Then allow the user to adjust any of these test parameters for the next test(s).
Q: What is the purpose of the Real-Time mode?
A: With a launch cable, the Real-Time mode may be used to quickly view many short fiber links. It can also be used to quickly “trace” short fiber links.
Q: Why do I need to use a launch and receive cable?
A: A launch cable allows the OTDR to settle down after the initial pulse and provides a reference cable for testing the first connector on the fiber under test. A receive cable provides a reference cable for testing the last connector of the fiber under test.
Q: Why should I average OTDR results from both ends (bi-directional averaging)?
A: In networks built with a mix of fiber types (older and newer fiber, G.652 and G.655 or G.657 fiber), an OTDR scan may show excess loss at a splice joining these fibers when viewed in one direction, and may show “gain” (negative loss) when viewed in the opposite direction. The actual splice loss can be computed by averaging the excess loss in one direction with the gain in the opposite direction. If the average loss meets the carrier’s splice acceptance criteria, there is no need to re-splice the connection, even though the excess loss when viewed in one direction exceeds the splice acceptance criteria. Bi-directional averaging automatically pairs traces taken from both ends, averages them and presents the averaged results.
Q: To perform bi-directional averaging, must both traces be obtained using the same OTDR?
A: Two different M310s may be used to acquire the results, but the results from both ends must be available in one M310 for that M310 to perform bi-directional averaging. This is most easily accomplished if the same M310 is used to test from both ends.
Q: How should files be named so the M310 can automatically match results from both ends and perform bi-directional averaging?
A: There is no special naming convention required for automatically matching results from both ends. What is required is that the both tests are run, and results stored, in the same job\route\cable\ file. It’s preferable to run, and save, tests from both ends in the same fiber file, and use the same OTDR, for better results organization. After running the test with the OTDR at one end (say END1) the user must change the “OTDR Located At” in the Job Settings screen to the other end (END2 in this case) when running the test in the other direction. Bi-directional Analysis must be set to “ON” in the Events Setting Screen.
Q: Must the same OTDR settings be used from each end to perform bi-directional averaging?
A: Yes. The OTDR must be set to the same range and pulse width settings for both traces in order to average the results.
Q: If I use a launch fiber when testing from one end, must I also use a launch fiber of the same length when testing from the other end?
A: It is recommended that the same launch cable be used in both directions to ensure the greatest accuracy in the average Link Loss calculation. While in theory different launch cables (either of the same or different length) could be used in each direction the bi-directional averaging of Link Loss may be skewed by differences in connector losses between cables.
Q: If I use a receive fiber when testing from A -> B, must I also use a receive fiber of the same length when testing B -> A?
A: It is recommended that the same receive cable be used in both directions to ensure the greatest accuracy in the average Link Loss calculation. While in theory different receive cables (either of the same or different length) could be used in each direction the bi-directional averaging of Link Loss may be skewed by differences in connector losses between cables.
Q: If an event is detected in A -> B direction, but not in the B ->A direction, can results still be averaged? If so, how is the average loss computed for the event detected in one direction but missed in the other direction?
A: The “missing event” is added as a 0 dB loss event. The average loss is ½ the measured loss of the automatically detected event (Avg. = (measured + added 0 dB) / 2)
Q: If the fiber in A -> B direction was measured at a significantly different length than in the B -> A direction, can the traces be averaged?
A: No. If length in the second test direction is significantly different than the length measured in the first test direction then a screen will pop up indicating that the unit is unable to perform bi-directional analysis due the mismatch in link lengths.
Q: Why is macrobend detection only available in the QUAD and 1310/1550 nm single-mode M310s?
A: Microbends and macrobends result in excess loss in single-mode fibers at longer wavelengths. Consequently, microbend and macrobend detection is only available by comparing single-mode traces obtained at 1310 and 1550 nm.
Q: What are the criteria used by the M310 to detect a micro- or macrobend?
A: A micro- or macrobend event is detected when the loss of a point defect at 1550 nm exceeds the loss at 1310 nm by 0.2 dB or more.
Q: If a loss event is detected at 1550 but not 1310 nm, can a micro or macrobend still be detected?
A: Yes. In this case, the M310 will add a 0 dB loss event at 1310 and report the new event as a macrobend, assuming the loss at 1550 nm is ≥0.2 dB.
Q: How is a micro- or macrobend reported?
A: Micro/macrobends are indicated in the event table with an event type displayed as ![]()
C840:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: When using my C840s are connected together to perform AT, the units won’t link, why?
A: In order for the C-840 and C-850 units to link properly, both must be set to the same fiber type (MM or SM). One unit must be set on “Main” while the other unit is set for “Remote”. After properly cleaning all patch cords, they must be connected between the correct OLS port (MM or SM) of the Main unit to the OPM port of the Remote and the second jumper must connect between the correct OLS port (MM or SM) of the Remote back to the OPM port of the Main unit. In most cases, the C-850 is selected as the Main unit to store all test results. This allows the larger C-850 unit to stay stationary at the MDF, while the smaller C-840 is transported in the field to each IDF.
C850:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: When my C850s are connected together to perform AT, the units won’t link, why?
A: In order for the C-840 and C-850 unfdg to link properly, both must be set to the same fiber type (MM or SM). One unit must be set on “Main” while the other unit is set for “Remote”. After properly cleaning all patch cords, they must be connected between the correct OLS port (MM or SM) of the Main unit to the OPM port of the Remote and the second jumper must connect between the correct OLS port (MM or SM) of the Remote back to the OPM port of the Main unit. In most cases, the C-850 is selected as the Main unit to store all test results. This allows the larger C-850 unit to stay stationary at the MDF, while the smaller C-840 is transported in the field to each IDF.
Q: What OTDR have TIA standard certification and troubleshooting capabilities?
A: The C-860 QUAD OTDR and Certification Test Kit is the best choice.
C880:
Q: I am working with SC-UPC to ASC panels and needed to set the reference with one patch cord. Can I plug the ASC directly into the SC cap for the OPM port?
A: Yes, OPMs are the only device that can accept both UPC and APC connectors using a single adapter cap. For example, an OPM with a SC adapter cap can accept both SC UPC and SC APC connectors. This is because the OPM does not have a ferrule inside of its test port. You are plugging into an adapter cap that suspends your connecter over a cavity, and the photo diode inside the cavity gathers all of the light from either type of connector.
Q: While testing angled SC connectors on my network, I keep getting bad results on my C880 kit.
A: Make sure you have not plugged angled SC plugs into the OLS port. When setting the reference and testing, pay careful attention to placing the ASC connectors only into the OPM port, not the OLS port, and your reference and test results work out OK. This will require using a hybrid UPC to APC launch jumper for each OLS port when testing angled connectors on your network.
Fiber Ring:
Q: Why do I need to use fiber rings?
A: Fiber rings allow the technician to measure the front panel and rear panel insertion loss and return-loss of the network under test. This will allow the technician to create a final report in TRM® that will show total Link Loss and Link ORL values.
Q: Why can’t I just use the launch cable and test the network from both directions?
A: Testing the network in both directions will confirm that the network may operate as designed, but will not allow TRM® to properly report Link Loss and Link ORL.
Q: How do I know which size fiber rings to use for my test?
A: The fiber rings must be longer than the length of the pulse of light by at least 1.5 times. This allows for the recovery of the attenuation dead-zone caused by the initial reflective spike located at the OTDR test port. The final patch panel also causes a reflective spike, which is why a receive cable must be used as well.
The length of the pulse of light may be calculated by dividing the PW in ns (nanoseconds) by 10. This will provide the approximate length of the pulse of light in meters.
Examples
- 100ns/10 = 10-meter light pulse. The standard 150-meter fiber rings will be adequate to test any fiber network at 100ns. The maximum PW that can be used with a 150-meter fiber ring is 1,000ns or 1.0µS.
- 1,000ns /10 = 100-meter light pulse. The 150-meter fiber ring is exactly 1.5 times the length of the pulse of light traveling down the fiber.
Refer to chart below for additional fiber ring and fiber box lengths:
Flex Tester:
Q: How do you setup the unit to tell it you have 2 or 3 splitters?
A: To test through multiple splitters, multiply together the split ratios and set the PON Split Ratio to that value. For example, if you have 1X8 followed by 1X8, set PON Split Ratio to 1X64. If you have 1X4 plus 1X8, set PON Split Ratio to 1X32. If you add 1X2 to this to create 1X2 + 1X4 + 1X8, set PON Split Ratio to 1X64.
Q: Is the Range value that you put in the range from the CO to the first splitter?
A: When Test = Through Splitter, the Range should be set to slightly exceed the distance from ONT (at customer premise) to OLT (at central office/local exchange). We usually recommend 25-30% longer than the network length. Max PON length is 20 km. Available Range selections are: 250 m, 500 m, 1000 m, 1.5 km, 3 km, 6 km, 15 km, 30 km. FLX380/OFL280 will automatically select pulse width and resolution settings based on the Range and PON Split Ratio. The table below shows the Pulse/Resolution settings for FLX380.
You can see that as longer range or higher split ratio is selected, wider pulse or Normal resolution is selected to achieve greater dynamic range needed to test through higher split ratios or longer networks. If a user is not happy with the results they get using the selected Range & PON Split Ratio, they can adjust the Range or PON Split Ratio setting to force a wider pulse width (for a less noisy trace) or a narrower pulse width (to see closely spaced events more clearly before the splitter(s)).
Q: If shooting from the customer ONT, is the Range the distance from ONT/ONU to the splitter?
A: If you only wish to test from the ONT to the splitter (not through the splitter), you can either use PON OTDR with Test = Customer Fiber Only, or you can use Full Auto (Point-to-Point).
Q: When purchasing a FlexTester, should I order UPC or APC ports?
A: To determine if an OTDR should have UPC or APC test ports, it is helpful to know if most of the networks to be tested will be UPC or APC. Since an OTDR is almost always used with a launch cable, it is the launch cable that does any necessary conversion from one connector style to another. Having the test port match the network connector style, UPC or APC, simply means the technician will need fewer different types of launch cables, but it does not preclude testing all types of network connections. For example, an FLX380 with an APC test port would require launch cables with at least one APC connector to be directly attached to the OTDR port. The other end of the launch cable can be either UPC or APC, depending on the network to be tested. If most of the networks are APC, then most of the launch cables would be APC on both ends, allowing them to have two connector types, such as SC/APC and LC/APC. This would allow testing of both SC and LC networks, simply by swapping ends of the launch cable and changing the OTDR adapter cap. Note that it is not the adapter cap that determines if a port is APC or UPC; it is the ferrule inside the unit. This means the OTDR is manufactured with either an APC or UPC ferrule. All OTDR adapter caps fit both styles. If the FLX380 is UPC, then the opposite would apply regarding the launch cables to be used.
Q: Does the Flex Tester test for Optical Return Loss?
A: The FLX380 does test for ORL. If launch and receive cables are used, ORL measurement excludes contributions from the launch and receive cables, as well as any excess reflection from the open end of the far-end receive cable.
Q: In the three wavelength models, if a fiber is shot in all three wavelengths, are the traces saved as one file or three different files?
A: Tri-wavelength test results are saved in three separate .SOR files, all having the same prefix.
Q: Can the traces be saved directly to an external flash drive or do they have to be saved on the OTDR then transferred to a computer later?
A: FlexTester results cannot be saved to an external flash drive, so they do have to be stored internally then transferred to computer later.
Q: How do I enable or disable the Launch Quality Check?
A: Launch Quality Check may be enabled/disabled from the Settings menu (accessible by pressing right tab key (→) when the Main Menu is displayed).
Q: What are the criteria for determining poor launch quality?
A: Poor launch quality is detected if loss at the OTDR connector exceeds approximately 0.9 dB, or the reflectance at the OTDR connector exceeds approximately -40 dB.
Q: What are the possible causes for poor launch quality?
A: Poor launch quality is likely due to one of the following problems:
- Dirty or damaged connector on the OTDR or mating connector on the launch cable or jumper attached to the OTDR;
- Mismatched connector types; e.g. OTDR is built with UPC connector, but is mated to an APC connector on the attached launch cable or jumper (or vice versa);
- OTDR connector adapter is loose, creating an air gap between the OTDR connector and the attached launch cable or jumper.
Q: What should I do if poor launch quality is reported?
A: Perform the following steps:
- Inspect and clean both the OTDR connector and the launch cable or jumper connector.
- If a short jumper was used, also inspect and clean the connection between the jumper and the network under test.
- Verify OTDR and launch cable or jumper both have the same connector type (UPC or APC).
- Verify the OTDR connector adapter is tight (turn clockwise to tighten).
- Press the “Re-check” softkey to repeat the launch quality check. If launch quality is now OK, OTDR test will initiate.
Q: What should I do if I’ve inspected and cleaned the connectors, verified connectors are both of the same type (UPC or APC), and verified the OTDR connector adapter is tightened, but poor launch quality is still reported after re-checking?
A: It is possible that connection quality at the OTDR is marginal (e.g. loss slightly greater than 0.9 dB or reflectance slightly higher than -40 dB), either due to wear-and-tear on connectors, or because the combined loss or reflectance of a short jumper with mated connections at both ends exceeds the launch quality loss or reflectance threshold. In this case, you may override the launch quality check and continue testing by pressing the Test key. However, you should review OTDR trace to ensure excess reflection (large reflective peak with long recovery tail) or excess loss at the OTDR connection is not producing poor test results.
Q: Can I continue an OTDR test even if poor launch quality is reported?
A: Yes, you can continue an OTDR test by pressing the Test key. This is not recommended unless you’ve already cleaned both the OTDR and launch cable connections, verified no connector mismatches, and verified OTDR connector adapter is tight.
Q: Can I obtain good OTDR results if I continue a test when poor launch quality is reported?
A: You can obtain good OTDR test results If launch quality is marginal (e.g. loss at front panel is slightly greater than 0.9 dB or reflectance is slightly greater than -40 dB). However, if excess reflection and/or loss occurs at the OTDR connector (e.g. due to dirt, damage, or an air gap), you likely will not obtain good OTDR test results.
Q: How do I enable/disable automatic macrobend detection?
A: From the OTDR Test screen, press the tab key (ï or ð) to select Events tab. Scroll down to highlight Macro-bend detection setting and press the left or right arrow key (| or }) to enable or disable macro-bend detection.
Note: Macro-bends can only be detected when OTDR test uses two or three wavelengths, such as 1310/1550 or 1310/1550/1625.
Q: Why must I test using at least two wavelengths to detect macro-bends?
A: Loss due to macro-bends is higher at longer wavelengths. Macro-bends are detected by comparing loss of a non-reflective event at a short wavelength (such as 1310 nm) to the loss at a longer wavelength (such as 1550 or 1625 nm). If the loss at longer wavelength is appreciably higher than the loss at the short wavelength, the event is identified as a macro-bend.
Q: Why does the OTDR sometimes detect and report a macrobend at 1550 nm, but reports no event at the same location at 1310 nm?
A: Often, the loss at 1310 nm due to a macro-bend will not exceed the event detection threshold, while the loss at 1550 nm does exceed the event detection threshold. In this case, the event will be reported in the 1550 nm results, but not the 1310 nm results.
Q: Why does the OTDR occasionally report a macrobend at 1550 nm, but reports the same event as the end of fiber at 1625 or 1650 nm?
A: Since bending loss is higher at longer wavelengths, it is possible for the loss due to a macro-bend to exceed the end detection loss threshold at 1625 or 1650 nm, while not exceeding the end detection threshold at 1550 nm. In this case, the event may be reported as a macro-bend at 1550 but as the end of fiber at 1625 or 1650 nm.
Q: Why am I getting an indication of Poor launch condition, even though the ferrules look good on inspection?
A: The FlexTesters will report poor launch quality if one or both of the following conditions is met:
- Loss at OTDR exceeds 0.9 dB
- Reflectance at OTDR exceeds -40 dBQ:
Q: I noticed the dead zone for this OTDR is 0.8m. How we determine this value?
A: Event dead zone is defined as, “Typical distance between the two points 1.5 dB down each side of a reflective spike caused by a -45 dB reflective event using 5 ns pulse width.” In practice, this means that two clean, mated PC connections 0.8 m apart can be visually detected in the trace since there would be a ‘valley’ between the peaks due to each reflective connection. All OTDR manufacturers use this (or a similar) definition of event dead zone. All OTDRs only meet their dead zone specs when their narrowest pulse is used. It is rare for an OTDR’s fault location algorithms to automatically detect two events this close together.
Q: Many PCs (mine included) often seem to want to install a new driver when I connect FLX380 or OFL280. When this occurs, it often takes 2-4 minutes for driver to install before PC recognizes FLX380 or OFL280. The solution is to wait for driver to install. How can I get my PC to retain the drivers?
A: While newer OFL280 and FLX380 units are shipped with a different USB chip which has improved speed and operation of USB interface, we still have the issue of PCs re-installing driver when FLX380 or OFL280 plugged in. We cannot control this (it is a PC issue). So users must simply wait for driver to be installed or recognized.
OFL250/OFL 280 Tester:
Q: Does the OFL test for Optical Return Loss?
A: While the OFL250 does not test for ORL, the OFL280 does test for ORL. If launch and receive cables are used, ORL measurement excludes contributions from the launch and receive cables, as well as any excess reflection from the open end of the far-end receive cable.
Q: In the three wavelength models, if a fiber is shot in all three wavelengths, are the traces saved as one file or three different files?
A: Tri-wavelength trace is saved as three separate .SOR files with the same prefix.
Q: Can the traces be saved directly to an external flash drive or do they have to be saved on the OTDR then transferred to a computer later?
A: FLX/OFL traces cannot be saved to an external flash drive, so they do have to be stored internally then transferred to computer later.
Q: How many traces can be saved in the OFL280 memory?
A: Formatted storage drive = 3.78GB in FAT 32, Optic version = 96KB, Software = 1.31MB, Each trace = 60KB in size, so potential storage capacity if 100% of the space could be used is > 63,000 traces.
Q: Is there any option to add more memory?
A: There is no option to add memory, but over 60,000 traces should be enough, even if they are all tri-wavelength.
Q: In the OFL280, why is the lowest splitter count in Auto Mode 1 x 8?
A: In FTTx - PON Construction test mode, the minimum split ration may be 1 x 8, but it will detect all splitters up to and including 1 x 8. So even if the splitter was a smaller 1 x 4 value, the 1 x 8 setting would be the appropriate setting to detect that splitter. The same would hold true if I set the ratio to 1 x 16 to detect a 1 x 8 splitter, it would work fine.
Q: How long will the VFL on the OFL280 stay transmitting?
A: It depends on the OFL280; earlier models turned off the VFL in about 10 minutes. An upgrade to v1.2.02 eliminated the VFL auto-off capability.
Q: What wavelengths does the OFL Light Source (OLS) provide?
A: The OFL280-102 offers 1310/1490/1550 source operation. The OFL280-103 only offers 1310/1550, while FLX380-303 and FLX380-304 offer 1310/1550/1625 nm source operation, respectively. This was to maintain consistency with past OFL280-103 operation.
