AN-103
Measuring Insertion Loss/Return Loss For Unlike Connectors
Using a Golden Cable and Bi-Directional Return Loss Meter
Over view
Testing hybrid cables poses certain difficulties due to the ends having unlike connector types. Typically hybridbulkheads/adapters are required (SC-FC, ST-FC, etc.) and many times they solve the problem with minor
issues. However, in some circumstances hybrid bulkheads will not suffice.
When testing SC-LC cables, such an instance arises. SC-LC bulkheads have high loss and poor repeatability
and as such, they should not be used in the testing process. To get around this issue, the golden cable
method can be used.
NE W

Referencing

Referencing Insertion Loss with Golden Cable
Similar to testing a DUT on the OP931, connect thegolden cable between the two reference cables (FC/APC-SC/PC on A-B source 1 and FC/APC-LC/PC
on B-A source 2 ).The golden cable should act as
connection between SC-LC without using the high loss
bulkhead.
Press Ref. to reference IL in both the A-B
NE W
and B-A directions. (To view this on the front panel,press the left arrow twice from the OPM screen to IL).

12
OP931

LC / LCSC / SC
Ref. Cable
ARef. Cable
BGoldenCable

Figure 1

Referencing Return Loss

OP931

Figure 2
Disconnected

To reference RL, press the left arrow once to the RL screen
from the IL screen. Disconnect the golden cable from bothreference cables and leave the LC and SC endfaces open
to induce a sufficiently large reflection. Press and hold
Ref until you see Ref: A---- on the front panel screen. This
indicates that the OP931 is searching for a large reflectionand determining the length of the reference cables. After
referencing, the instrument will continue measuring returnloss on both wavelengths automatically.

Testing the DUT
Attach the DUT between the reference cables (where thegolden cable used to be) and IL and RL readings should
start automatically without any further calibration. Toview both measurements, navigate to either IL mode or
RL mode.

OP931

Ref.
Cable
ANE W

1

SANTEC CORPORATION
5823 Ohkusa-Nenjozaka, Komaki,
4750 Calle Quetzal
Aichi 485-0802,Camarillo,
CA Japan
93012

OptoTest Corp.

Doc:AN-103 Rev. A 5 /16 /13+81-568-79-3536

Figure 3

www.santec.com

LC / LCSC / SCRef.
Cable
BDUT

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

Measuring Insertion Loss/Return Loss For Unlike Connectors
Using a Golden Cable and Bi-Directional Return Loss Meter

AN-103

Concerns When Using the Golden Cable Method
It is possible that if the golden cable is not reference quality, the DUT will actually display gain rather than aloss. This is due to a non-reference quality cable being replaced with a better, low loss DUT. Therefore, thegolden cable should have low loss to see a negative value when testing the DUT. However, even when a lowloss reference grade golden cable is used, it is still possible to measure zero insertion loss or even a positive
NE W
insertion loss when measuring a DUT. This may be due to either the reference being done poorly because ofdirty connectors or bad bulkheads or that the DUT is actually of higher quality than the golden reference cable.
NE WGolden Cable Verification

SC/PC to2 .5mm
OPMAdaptor

A golden cable would be a reference-quality cable with
low insertion loss. Before referencing for the DUT, one
should verify that the golden cable has fairly low loss(<0.05 dB).
This requires a simple insertion loss test with the golden
cable as the DUT and two OPM adapters, 2.50mm and1.25mm.
First, attach the 2.50mm adapter to the OPM
NE Wand connect the FC/APC side of the reference cable on
the AB source port 1 and the SC/PC end to the 2.50mm
adapter 1 . Click Ref.

1LC/PC to1. 25mm
OPM Adaptor

OP931

GoldenCable
SC / SCFigure 5

11OP931

Figure 4
Ref. Cable

Remove the 2.50mm adapter and connect the 1.25mm
adapter to the OPM. Now connect the SC/PC side of
the golden cable to the reference and the LC/PC end
to the 1.25mm adapter 1 to test its reference quality.
Readings should start automatically and can be seenin the IL screen by pressing the right arrow button
once from the OPM screen.

Ref. Cable
ALC/PC to
1. 25mm
OPM Adaptor

To reference the LC/PC side of the cable, switch out
the reference cable for LC/LC testing and connect
it to the AB source port and the LC/PC end to the
1.25mm adapter 1 . Click Ref.

1OP931Figure 6

11OP931

Figure 7

2

SANTEC CORPORATION
5823 Ohkusa-Nenjozaka, Komaki,
4750 Calle Quetzal
Aichi 485-0802,
Camarillo,
CA Japan
93012

Ref. Cable

SC/PC to2 .5mm
OPM Adaptor

GoldenCable
LC / LC

Similar to testing the SC end of the cable, disconnect
the 1.25mm adapter 1 and attach the 2.50mm adapter
to the OPM and connect the LC/PC side of the golden
cable to the reference and the SC/PC end to the2.50mm OPM adapter 1 to test its reference quality.

OptoTest Corp.

Doc:AN-103 Rev. A 5 /16 /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