Testing Short SM DUTs
with the RL1

Testing Short SM DUTs with the RL1
One of the advantages of the RL1 compared to traditional OTDR IL/RL meters is its ability to measure the total
return loss (RLTotal) of a single-mode (SM) device under test (DUT).
Because RLTotal has no dead-zone, it is ideal for measuring short DUTs like cassettes. In this document, we willshow how to measure a typical short SM DUT using the RL1 Automated Return Loss Meter and JGR’s freesoftware, GMS.
You can download GMS on our website: https://jgroptics.com/downloads/software
If you have any questions, please email support@jgroptics.com
DUT Details• 30 cm cassette• 12 fibers (SM)• MPO/APC to LC/PC

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Equipment Required• RL1 IL/RL meter• SX1 switch• Computer or tablet with GMS software© JGR Optics Inc.

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Testing Short SM DUTs with the RL1
Test Parameters• ILTotal: because of the closed configuration of a cassette, it is not possible to insert the connectors intothe detector. It is therefore standard practice to measure the total insertion loss (ILA + ILB) of the DUT.
•RLTotal: for some DUTs shorter than 1.7m, it is not possible to accurately measure the return loss of eachconnector separately without terminating the far end. With the RL1, you can measure the total returnloss (RLA + RLB + fiber) of the DUT without the need for termination.

Hardware Setup (option #1: USB)
• Connect the SX1 directly to the RL1 via USB.
• Connect the RL1 directly to the PC or tablet via USB.

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Testing Short SM DUTs with the RL1Hardware Setup (option #2: Ethernet)• Connect the SX1 directly to the RL1 by USB.
• Connect the RL1 and PC to a LAN via Ethernet.

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Testing Short SM DUTs with the RL1
GMS: Establishing Communications• Launch GMS and go to Settings > Instrument Settings.

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Testing Short SM DUTs with the RL1
GMS: Establishing Communications
1. Use the settings below and select the appropriate port (USB or Ethernet) for your setup.
2. Use the drop-down menu to select the RL1’s IP address or USB port. If your network settings preventthe auto-discover function for Ethernet, manually enter the IP address of the RL1.
3. Click Test Port.

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2

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Testing Short SM DUTs with the RL1
GMS: Establishing Communications•You will get a pop-up confirming the active status of the instrument and be prompted to automaticallydetect the wavelengths. Click Yes.
•The software will automatically detect the switch’s number of channels and the RL1’s number ofdetectors and wavelengths.
•Click OK.

If you have more than one
switch connected, use the dropdown menu to select theappropriate one and click Test
Port to confirm.

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Testing Short SM DUTs with the RL1Reference•
Inspect and connect an FC/APC to FC/APC SM jumper between the RL1 output and the SX1 common.
•Inspect and connect a 12*FC/APC to MPO/APC SM fanout between the SX1 outputs and the RL1detector.
o The length must be at least 3m.
o The fanout will act as the master test jumper (MTJ) or reference cable.
o Short protection or sacrificial jumpers can be used before the MTJ but the last cable before theDUT must be at least 3m.

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Testing Short SM DUTs with the RL1
RL1 Reference page
showing stored values

Reference

SD17
MTP/MPO slide
detector adapter

CS400K-CM
Benchtop 400x
inspection scope

RD-S
Remote-headdetector

MTJ 1
12*FC/APC to
MPO/APC fanoutwww.jgroptics.com© JGR Optics Inc.

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Testing Short SM DUTs with the RL1
Reference•Insert the sequences below.
1. The RL1 requires an IL reference for each channel and wavelength.
2. The RL1 requires a length reference for each channel but only one wavelength.
•You can save the profile for future use (File > Save Profile as…).

1

2

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Testing Short SM DUTs with the RL1
Typical values are < 1 dB.

If you have more than 2 dB in your reference IL value, it isrecommended to inspect each connector end face fromthe RL1 output to the end of MTJ 1.

Select Reference acquisitionand click on Start.
The reference values arestored on the RL1 meter.

Typical values are within+/- 0.2 m of each other.
Higher variations could
indicate a bad mating tothe switch output causinga very high reflection ordamaged fiber on theMTJ.

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Testing Short SM DUTs with the RL1
Measure•Disconnect MTJ 1’s MPO connector from the detector.
•Inspect and insert the MPO connector of MTJ 2 12*LC/PC to MPO fanout in the detector.
o The recommended length is 3m but it can be longer.
•Inspect and connect the DUT MPO/APC to 12*LC/PC cassette between MTJ 1 and MTJ 2.
o There is no minimum length for the DUT.

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Testing Short SM DUTs with the RL1Measure•
The RL1’s detection algorithm automatically identifies the DUT. It measures the total return loss of thedevice without needing to set a measurement window thereby eliminating operator error andsimplifying the testing process.
•While it includes a small amount of fiber reflection of each MTJ, it is negligible compared to the DUT.
•No physical termination required and the detector side MPO connector can be either APC or PC.

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Testing Short SM DUTs with the RL1
RL1 Measure page showing
the last measured channel

Measure

MTJ 1
12*FC/APC to
MPO/APC fanout

MTJ 2
12*LC/PC to
MPO/APC fanoutwww.jgroptics.com

DUT
MPO/APC to
12*LC/PC cassette© JGR Optics Inc.

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Testing Short SM DUTs with the RL1
Measurement
1. Click in the top left cell of the sequence window to select all then press Delete.
2. Select the parameters below then click Insert.

2

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Testing Short SM DUTs with the RL1
Measurement•Select the test parameters below then click Insert.
•You can save the profile for future use (File > Save Profile as…).

Make sure theacquisition mode isset to Measurementwww.jgroptics.com© JGR Optics Inc.

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Testing Short SM DUTs with the RL1
Click Start

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