AN-114
RL Testing for APC Terminated Cables
Over view
When referencing return loss, the OP930 scans a length of fiber and looks for a large reflection (~14dB or a 4%reflection). However, a reference cable that has an APC endface will not give a reflection large enough to trigger
the OP930 to reference. To fix this issue and to be able to measure DUTs with APC endfaces, two methods will
be discussed below that will allow the OP930 to perform a proper reference measurement.

NE WUsing an APC-PC Replacement Cable as Reference

The first method uses a PC-terminated cable which is the same length as the APC-terminated reference cable
to reference return loss.
Note: The APC-PC cable must be the same length (+/-0.1m) as the APC-APC cable in order to be substituted.

Return Loss Reference
NE W

Connect the APC endface of the APC to PC
substitute cable to the OP930 front panel andleave the PC endface unmated. Navigate to the RL
screen by pressing the right arrow button twicefrom the OPM screen and press and hold Ref. Theunit will then begin to look for the largest reflection
and then it will begin taking measurementsfrom that distance. The reference measurement
should be approximately 14 dB. The length will be
displayed above the measurements. If using an
APC-APC, the RL screen would read Error.

1310nm

RL

11.5 C-14.6

dBSource

RefDetectordBm

1310 /1550
1490/1625

OP930

IL/RL Test Set

Figure 1: An OP930 with an UPCterminated HPR cable connected for
RL reference.

HPR

PC

Now that the return loss reference distance has been found, the APC-PC cable can be switched for the APC-APC
reference cable.
1310nm

RL

11.5 C-65.3

dBRefSource

Detector

dBm

1310 /1550
1490/1625

OP930

IL/RL Test Set

Figure 2: The UPC-terminated HPR isswapped out for the APC-terminated HPR.
HPR
* HPR: High Per formance Reference Cable

1

SANTEC CORPORATION
OptoTest
Corp.

5823 Calle
Ohkusa-Nenjozaka,
Komaki,
4750
Quetzal
Aichi 485-0802,
Japan
Camarillo,
CA 93012
Doc:
AN-114 Rev. A 7/11/13+81-568-79-3536

www.santec.com

APC

SANTEC USA CORPORATION
8 05.987.170 0
USA Toll Free
+1-800-726-8321
sales@ optotest.com
engineering @ optotest.com
SANTEC EUROPE LIMITED
Tel. +44-20-3176-1550

AN-114RL Testing for APC Terminated Cables
Insertion Loss Reference
1310nmIL

With the APC-APC launch cable connected to the source,
insertion loss can now be referenced. Since insertion
loss does not need a PC endface for reference, simplyconnecting the unmated side of the cable to the detector
will gather sufficient data. Navigate from the RL screen
to the IL screen (press the left arrow button once) andpress Ref. This will take absolute reference in dBm of all
wavelengths and display relative wavelength in dB on thescreen. The absolute reference value will be displayed insmaller text above the relative measurements.

11.5 C

0.000

dBSource

RefDetectordBm

NE W
1310 /1550
1490/1625

OP930

IL/RL Test Set

HPR

Figure 3: The APC-terminated HPR is then connectedto the detector for the IL reference. After this step iscompleted, the DUT can be connected as normal.

Using an APC-APC Cable as Reference
The second method uses a very short APC-to-PC (3 to 6in) cable connected to the APC-terminated reference
cable to produce a large enough reflection to reference return loss.

Return Loss Reference
Connect one endface of the reference cable to theNE W
OP930
front panel and connect the other end to
the APC endface of the reference reflector, leaving
the PC endface of the reference reflector unmated.
Navigate to the RL screen by pressing the rightarrow button twice from the OPM screen and press
and hold Ref. The unit will then begin to look forthe largest reflection and then it will begin taking
measurements from that distance. The reference
measurement should be approximately 14 dB. The
length will be displayed above the measurements.

1310nm

RL

11.5 C-14.6

dB

SourceRefDetectordBm

1310 /1550
1490/1625

OP930

IL/RL Test Set

HPRAPCPC

Figure 4: Instead of using a substitute cable, this method utilizes a shortreflector stub to create a large reflection near the end of the HPR.

Now that the return loss reference distance has been found, the reference reflector can be removed from the APC-APC
reference cable.
1310nm

RL

11.5 C

-65.3

dB

Ref

SourcedBm

1310 /1550
1490/1625

OP930

IL/RL Test Set

2SANTEC CORPORATIONOptoTest
Corp.

Figure 5: After referencing RL, thereflector stub should be removed fromthe HPR.

5823 Calle
Ohkusa-Nenjozaka,
Komaki,
4750
Quetzal
Aichi 485-0802,
Japan
Camarillo,
CA 93012
Doc:AN-114 Rev. A 7/11/13+81-568-79-3536

Detector

HPR

www.santec.com

APC

SANTEC USA CORPORATION
8 05.987.170 0
USA Toll Free
+1-800-726-8321
sales@ optotest.com
engineering @ optotest.com
SANTEC EUROPE LIMITED
Tel. +44-20-3176-1550

AN-114RL Testing for APC Terminated Cables
Insertion Loss Reference
1310nmIL

11.5 C0.000

With the reference reflector removed, simply
connect the unmated APC endface of the cable tothe detector to reference insertion loss. Navigatefrom the RL screen to the IL screen (press the left
arrow button once) and press Ref. This will takeabsolute reference in dBm of all wavelengths anddisplay relative wavelength in dB on the screen.
The absolute reference value will be displayed insmaller text above the relative measurements.

dBSource

RefDetector

dBm

APC
1310 /1550
1490/1625

OP930

IL/RL Test Set

NE W

HPR

Figure 6: Once the reflector stub is removed, the HPR
can be connected to the detector for an IL reference.

Testing
1310nm

RL

11.5 C-78.3

dBRefSource

A DUT can now be attached between the launch
cable and the OPM and testing can begin. The OP930
automatically begins taking measurements as soon asa reference is found.

Detector

dBm

OP930

IL/RL Test Set

APC1310 /1550
1490/1625

NE WHPR
APC

Figure 7: After the IL reference has been completed, the DUT
can be connected as normal.

To view insertion loss and return loss measurementssimultaneously for one wavelength, navigate to theILRL screen by pressing the right button once fromthe RL screen. To view insertion loss measurements
for two wavelengths at the same time, navigate to theIL2 screen by pressing the right button twice fromthe RL screen. To view insertion loss and return loss
measurements simultaneously for two wavelengths,
navigate to the ILRL2 screen by pressing the rightbutton three times from the RL screen.

Using a Multifiber APC-APC Cable with Reference Reflector
The same principles can be applied to multifiber cables as with simplex cables; both the replacement cable method
and the reference reflector method work, but it is suggested that the reference reflector method be used. A multifiberreference reflector will provide a much more accurate reference than the replacement cable because the possible
variation in the cable lengths within the fiber ribbon. For more information on MTP reference reflectors, please see
our Application Note AN-115 Referencing Return Loss Using the MTP Reference Reflector.
NE W

3SANTEC CORPORATION
OptoTestCorp.

5823 Calle
Ohkusa-Nenjozaka,
Komaki,
4750
QuetzalAichi 485-0802,
Japan
Camarillo,
CA 93012
Doc:AN-114 Rev. A 7/11/13+81-568-79-3536

www.santec.com

SANTEC USA CORPORATION
8 05.987.170 0
USA Toll Free
+1-800-726-8321
sales@ optotest.com
engineering @ optotest.com
SANTEC EUROPE LIMITED
Tel. +44-20-3176-1550