OTDR, short for optical time-domain reflectometer, is an optoelectronic instrument used to characterize an optical fiber. … OTDR injects a series of optical pulses into the fiber under test. It also extracts, from the same end of the fiber,light that is scattered or reflected back from points along the fiber.
How does OTDR calculate distance?
The OTDR is measuring the length of the fiber you are testing – not the physical cable. An OTDR uses the fiber’s “index of refraction” (IOR) value to calculate distances. … Performing an OTDR test on each cable spool and reporting the cable markings on each length of cable are essential.
What does the OTDR measure?
The OTDR measures distance and loss between the two markers. This can be used for measuring loss of a length of fiber, where the OTDR will calculate the attenuation coefficient of the fiber, or the loss of a connector or splice.
How do you use OTDR?
- Turn on OTDR and allow time to warm-up.
- Clean all connectors and mating adapters.
- Attach launch cable to OTDR. Attach receive cable (if used) to far end of cable.
- Set up test parameters on OTDR.
- Attach cable to test to end of launch cable. Attach receive cable (if used) to far end of cable.
- Acquire trace.
What is a gainer on an OTDR trace?
Akin to water flowing from a small pipe into a large pipe, gainers are essentially perceived increases in optical power that occur at splice points due to variations in fiber characteristics, including core diameter, numerical apertures, mode field diameters and backscatter coefficients.
What is the dead zone in OTDR?
The OTDR dead zone refers to the distance (or time) where the OTDR cannot detect or precisely localize any event or artifact on the fiber link. It is always prominent at the very beginning of a trace or at any other high OTDR reflectance event.
What is pulse in OTDR?
In an OTDR, the pulse carries the energy required to create the backreflection for link characterization. The shorter the pulse, the less energy it carries and the shorter the distance it travels due to the loss along the link (i.e., attenuation, connectors, splices, etc.).
What is an acceptable dB loss on fiber?
0.5 dB per km @ 1550 nm. These are the minimum requirements. Be aware that fiber specifications typically contain tighter values. For instance, 0.5 dB per mated connector and 3.0 dB per km @ 850 nm.
How far maximum km can test with OTDR?
A: A 1.0 µs (1,000 ns) pulse width will test up to 40 km of Corning SMF-28e fiber @1310 nm and 50 km @ 1550 nm.
How long does OTDR testing take?
It typically takes at least 3 minutes for a skilled OTDR technician with high-quality equipment to obtain one trace. Printing out the trace adds another 2 to 3 minutes per fiber. In a system of only 48 fibers, this adds approximately 5 man-hours, including set-up time, to the testing procedure.
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How do I set up OTDR?
To select Manual OTDR mode, turn the rotary switch to AUTOTEST, press F3 Change Test; then select Manual. You can access these settings on the Fiber OTDR tabs in Setup. Tip: To see the settings used for an OTDR test, press F2 View Events on the OTDR Results screen, press F3 View Details; then press F1 OTDR Settings.
What wavelength is used for OTDR testing?
OTDR users generally used the two-wavelengths provide the best balance of functionality and value. OTDR testing at 1310 nm and 1550 nm is normally sufficient to certify point-to-point or FTTx PON fibers and allows the detection of macro bends.
What is a good fiber dB reading?
The optical power meter usually reads in dBm for power measurements or dB with respect to a user-set reference value for loss. … For multimode fiber, an OLTS using a LED source will usually measure over a range of 0-30 dB, more than adequate for most multimode cable plants which are under 10 dB loss.
Who invented OTDR?
Using a tank of water with a pipe that ran out of one side, Babinet then shone a light into the tank, into the stream of water. An arc of light followed the water as it fell. An optical telephone system was patented in 1880 by Alexander Graham Bell.
What is typical splice loss of the joint?
The observed average splice loss at 1310 nm is 0.054 dB with SD of 0.015 dB, while at 1550 nm the average splice loss and SD is 0.045 dB and 0.014 dB, respectively.
What is splicing in OFC?
Simply put, fiber optic splicing involves joining two fiber optic cables together. The other, more common, method of joining fibers is called termination or connectorization. … Splicing is also used to restore fiber optic cables when a buried cable is accidentally severed.
How will you differentiate between a bend & A splice with an OTDR?
The bending looks almost the same as splice, but with one small difference. Splice will produce approximately the same attenuation at both wavelengths. In the case of the fiber bending, the measurement at 1310 nm will not show it at all, or make it poorly visible, and at 1550 nm will produce several decibels!
What is OTDR dynamic range?
The dynamic range of an otdr is the difference between initial backscatter and the noise level, which can be taken either as 98% or rms value. Measurement range is more application-oriented. Also given in decibels, it is defined as the maximum attenuation between the front connector and an event, i.
What is the use of launch cable in OTDR?
The launch cable allows the OTDR trace to settle down after the test pulse is sent into the fiber so you can analyze the beginning of the cable you are testing.
What is the lowest attenuation dB of a 1 km length fiber?
Fiber TypeWavelengthFiber Attenuation /km (1)Multimode 62.5/125um850nm3.5 dB1300nm1.5 dBSingle Mode 9um1310nm0.4 dBSingle Mode 9m1550nm0.3 dB
What causes negative loss in fiber?
Negative loss, or gainers, can also occur due to differences in connected fibers. If the two fibers have different backscatter coefficients (a fancy term for information about the relative backscatter level of the fiber), more light can be backscattered after a connection rather than before the connection.
What is fiber margin?
In an optical communications link, the optical power margin is the difference between the optical power that is launched by a given transmitter into the fiber, less transmission losses from all causes, and the minimum optical power that is required by the receiver for a specified level of performance.
Can you OTDR multimode fiber?
Some multimode OTDRs are now usable for short length multimode premises cables but only if they are properly set up before use. … The launch cable also allows the OTDR to check the first connector on the fiber being tested. An OTDR must always be used with a launch cable that matches the fibers being tested.
How do I reset my OTDR?
- Press Menu and select Setup > Power Meter, and then press Enter. OR. From the Power Meter pane, press Setup (F1/F2 key).
- Press Factory Settings (F1/F2 key).
- Answer Yes to confirm.
