AN145

The Photonics Pioneer

Measuring ILRL and Verifying Polarity With the Same Setup
Overview
Polarity testing and Insertion Loss (IL) testing are crucial steps in the production and assessment of multi-stranded fiber opticcables. With certain setups, IL can be measured while verifying polarity.
The IL test measures the amount of light lost when traveling through the DUT en route to the detector. A test setup that uses
a multichannel source and multichannel power meter evaluates the light paths of a multifiber device under test (DUT) one at atime. If any of the fibers are crossed or broken, light does not reach the OPM on the expected channel resulting in dark values.
Using an Insertion Loss and Return Loss (RL) meter as the source instrument and a multichannel power meter as the detector
allows for 3-in-1 IL, RL, and polarity evaluation.

Equipment Setup
See the following table for a full list of equipment options for creating an IL, RL, and polarity test setup. This application note
focuses on the multichannel OP940 and the OP710 for testing multimode 50um MPO assemblies. Figures 1 and 2 show thelaunch and receive cables used with this equipment. The launch reference cable is a standard high performance (HPR) fanout
cable with a type A mapping and 50um fiber. In order to route each fiber of the MPO to individual power meters, a fanout receive
cable is needed as well. A “large core” receive cable, 62.5um in this case, acts as a “zero” loss connection. One could use a 50um
receive cable here as well, but sometimes the additional loss causes referencing errors that could lead to negative IL values (gainmeasurements).

Referencing Process
The RL reference is performed by leaving the HPR launch cable open to air. This allows the OP940 to find the location of the DUT.

Reference Cable

Large Core
Receive Cable

Figure 1: Return Loss reference setup. The launch and receive cables are disconnected and the launch cable connector is open to air.

The IL reference is performed by mating the HPR launch cable to the large core receive cable using a type A mating adapter. Thisadapter creates a key-up to key-down connection and maintains a one-to-one polarity.

1OptoTest Corp.

SANTEC
4750
CalleCORPORATIONQuetzal
5823
Ohkusa-Nenjozaka,
Komaki,Camarillo,
CA 93012
Aichi 485-0802,
UnitedStates Japan+81-568-79-3536

Doc: AN-145 Rev. A 10/26/20

Advancing the World of Fiber Optics®
www.optotest.com
www.santec.com
The Photonics Pioneer

SANTEC USA CORPORATION
1.805.987.170 0
USA Toll Free
+1-800-726-8321
sales@optotest.com
suppor t@optotes t.com
SANTEC
LIMITED
MTP® is EUROPE
a registered trademarkof US Connec
Tel. +44-20-3176-1550

Measuring ILRL and Verifying Polarity With the Same Setup

AN-145

The Photonics Pioneer

Type A matingFigure 2: Insertion Loss reference setup. The launch and receive cables are connected using a Type A (key up to key down) mating adapter.

The IL reference process measures power on each channel independently using the OP710. This independent measurement does
not allow an incorrectly routed DUT to measure correctly.

Measurement Process for Type A Assemblies
For the test step, connect the DUT between the launch cable and the large core receive cable.

DUTAB
Type A mating

Type A mating

Figure 3: Measurement setup. The DUT is mated to the launch and receive cables using Type A mating adapters.

Connecting the cables in this way measures IL and RL for side A. Side B does not contribute to the IL due to the large core receive
cable creating a zero-loss connection. IL and RL for side B are measured by flipping the DUT.
To measure side B, flip the cable.

DUT

B
Type A matingA
Type A mating

Figure 4: For side B measurement, simply flip the DUT.

Because a multichannel OPM is used with a fanout cable, the polarity is verified to be type A. A different mapping would result in“dark” values. The test setup as described above verifies a one-to-one mapping only.
SANTEC CORPORATION
5823 Ohkusa-Nenjozaka, Komaki,
Aichi 485-0802, Japan

2+81-568-79-3536

www.santec.com
www.optotest.com
The Photonics Pioneer

SANTEC USA CORPORATION
USA Toll Free +1-800-726-8321
SANTEC EUROPE LIMITED
Doc: AN-145 Rev. A 10/26/20
Tel. +44-20-3176-1550

Measuring ILRL and Verifying Polarity With the Same Setup

AN-145

The Photonics Pioneer

Measuring non-Type A Assemblies
A “deshuffle” cable can be used to test assemblies of a different polarity than type A. A deshuffle cable is a cable that inverses thepolarity change that occurs through the DUT and restores type A polarity through the receive cable. This inversion restores thelight path established during referencing in order to measure loss properly. Without this cable, a non-type A cable routes light tothe wrong OPM channels, leading to dark power readings.
The deshuffle cable has the same polarity as the DUT being tested. For instance, when testing a type B DUT the deshuffle cableshould also be type B. It is also recommended that the deshuffle cable have a larger core size than the DUT to reduce loss andisolate the IL measurement to the connector on the front of the DUT. In the case of a 50um DUT, a 62.5um deshuffle cable isrecommended.

AType B DUT

Type A mating

B

Type BDeshuffle

Type B mating

Type A mating

Figure 5: A 62.5um deshuffle cable is used to restore the polarity of the light path to type A when testing a 50um non-type A DUT.

In this test setup, side A of the DUT is still the connection that is being tested. Using large fiber cores for the deshuffle and receivecables maintains the zero loss connections in the later half of the setup. To test side B, the DUT must be flipped.
The same principles used to test the 50um DUT can also be applied to a single mode system. For a 9um single mode DUT,
50um multimode deshuffle and receive cables are appropriate for the large core setup. Note that single mode MPO assemblies
typically have angled connectors while multimode assemblies have flat connectors, so an angled MPO connector is needed tomate to the DUT.

Figure 6: The test setup for a non-type A single mode assembly. The deshuffle and receive cables
are 50um multimode and side A of the deshuffle cable has an angled connector.

SANTEC CORPORATION
5823 Ohkusa-Nenjozaka, Komaki,
Aichi 485-0802, Japan

3+81-568-79-3536

SANTEC USA CORPORATION
USA Toll Free +1-800-726-8321

www.santec.com
www.optotest.com
The Photonics Pioneer

SANTEC EUROPE LIMITED
Doc: AN-145 Rev. A 10/26/20
Tel. +44-20-3176-1550

Measuring ILRL and Verifying Polarity With the Same Setup

AN-145

The Photonics Pioneer

Measuring non-Type A AssembliesNote that for any polarity, even non-standard polarities, a cable of the same polarity can act as a deshuffle to re-route the links
to the proper channels for the optical power to be measured correctly. For this method, it is imperative that only type A mating
adapters be used. Any other type of mating adapter will switch the polarity of the setup and lead to confusing and incorrect
results.

Equipment Cable

DUT

De-shuffle

Receive Cable

Figure 7: Example type B polarity deshuffle.

Equipment Cable

DUT

De-shuffle

Receive Cable

Figure 8: Example Shuffle/Deshuffle for type C.

4

OptoTest Corp.

SANTEC
4750
CalleCORPORATION
Quetzal5823
Ohkusa-Nenjozaka,
Komaki,
Camarillo,
CA 93012
Aichi 485-0802,
UnitedStates Japan+81-568-79-3536

Doc: AN-145 Rev. A 10/26/20

Advancing the World of Fiber Optics®
www.optotest.com
www.santec.com
The Photonics Pioneer

SANTEC USA CORPORATION
1.805.987.170 0
USA Toll Free
+1-800-726-8321
sales@optotest.com
suppor t@optotes t.com
SANTEC EUROPE LIMITED
Tel. +44-20-3176-1550