Testing a Short Cassettewww.jgroptics.com

Testing a Short Cassette
Measuring RL on short DUTs (length < 1.7m) requires terminating the far end connector whenusing an OTDR based instrument (MS12). For cassettes, this is not always possible.
The most accurate method is therefore to measure BR of the whole DUT (for more informationon the differences, please see the application note “Backreflection vs Return Loss”).
This document will explain the correct method in measuring IL and BR of a short cassette using aJGR MBR5.
Using JGR’s free software, GMS, the testing can be automated. Typically, the testing time for IL
and BR at 2 wavelengths for 12 channels is < 30 seconds.
In this example, the DUT has the following properties:• MM (50um)• Side A: 24*LC/UPC• Side B: 2*MPO/PC(M)• Length = 0.2m

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Testing a Short CassetteIn order to measure total BR of the DUT, it must be connected to a launch master test jumper(MTJ 1) and a receive master test jumper (MTJ 2).
The far end connector of MTJ 2 must be terminated. This can be done by using index matchinggel/block or with an APC-to-air termination. Because the MBR5 uses OCWR technology, thelength of MTJ 2 should be as short as possible (ideally < 1m).
In this example,• MTJ 1 = 12*FC/APC – LC/UPC• MTJ 2 = MPO/PC(F) – MPO/APC• Testing will be done in 2 sequences: fibres 1-12 then 13-24

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Testing a Short Cassette
Reference Procedure:

MBR5 bulkhead inspection
using a handheld scope

1. Connect the MTJ 1 to the MBR5. Remember to inspect both ends
before connecting. This is especially important if connecting directly to theMBR5.
For maximum stability, use a heat gun to gently heat the fibres and avoid
sharp bends. See below.

✓✓
MTJ 1 connector inspection
using a JGR CS400K-CM

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Testing a Short Cassette
Reference Procedure
2. Attach the appropriate detector adapter (in this example, a magnetic LC detector adapter isused: MDA118).

Inspect/clean MTJ 1 and connect to the MBR5 detector. Press Ref to take a power reference.
Note: this can be done in BR or Power mode. Holding Ref for 2 sec will reference allwavelengths, holding it for 5 sec will reference all wavelengths and channels.

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Testing a Short Cassette
Reference Procedure
3. In BR mode, terminate the open MTJ 1 connector to take a BR0 measurement. Do this foreach wavelength and channel.

If using index matching, be sure to clean the connector after the BR0 measurement.
Note: it is critical to take an accurate BR0 measurement or there is a risk of false passes (a DUT
that should fail might pass). Termination techniques can vary but index matching gel or block is
typically the best. See the “How to Reference and Measure BR – MM BR5” tutorial for more
information on how to correctly terminate using index matching block.

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Testing a Short Cassette
DUT Testing Procedure
1. Inspect/clean and connect the DUT side A and MTJ 1.
2. Inspect/clean and connect the DUT side B and MTJ 2.
3. Connect the MTJ 2 open connector to the MBR5 detector using the appropriate detector
adapter (in this example, a magnetic MTP/MPO detector adapter is used: MDA117).

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Testing a Short Cassette
DUT Testing Procedure
4. Power mode will display the relative power of the DUT.
5. Go to BR mode and terminate the MTJ 2 open connector to display the BR of the DUT.
Note: if using APC-to-air termination, BR can be measured with the APC connector in the MBR5
detector.
This will add a small amount of reflection to the BR measurement. Since the displayed BR will beslightly worse, there is no risk of a false pass.
If a DUT fails but is close to the target specification, it is acceptable to take the APC connector
out of the detector and re-measure. This is the true BR value.

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Testing a Short Cassette
GMS Testing Procedure
Using GMS and an APC-to-air termination, a 12 fibre DUT can be tested for IL and BR at 2
wavelengths in under 30 sec.

For example, choose the test parameters below and press Insert. Pauses can be added before
select channels if using index matching for BR termination.

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