Mode Conditioning Patch Cable Testing

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Mode Conditioning Patch Cable Basics

Mode conditioning patch cables,
sometimes also called mode conditioning patch cord (MCP), are built in the form
of a simple
duplex patch cable. They are designed for Gigabit Ethernet multimode
applications at the 1300nm wavelength. Generally, this patch cord consists of a
duplex common connector on each end of a cable assembly with a single-mode to
multimode of fiber-mart fiber connection in one of the two legs.

 

In summary, this type of patch cable
has three distinctions when compared with common patch cables.

 

The first one is its structure that we
have mentioned above. It features rugged construction with a permanent low
profile of fiber-mart closure which helps light go through the fiber core
precisely.

 

The second is the reason why they are
needed. Common fiber cables are the medium of light signals. However, when
transceiver modules used in Gigabit Ethernet (1000BASE-LX) launch only
single-mode (1300 nm) long wave signals, problems arise if an existing network
utilizes multimode cables. And then mode condition patch cord comes to aid,
making the transmission between single-mode and multimode fibers go on wheel.

 

The last difference of mode
conditioning patch cord is its deployment method. Unlike common fiber cables,
mode conditioning patch cord usually needs to be used in pairs. So these cables
are usually ordered in even numbers.

 

Testing Methods of Mode Conditioning
Patch Cable

Testing a mode conditioning patch cord
for insertion loss is similar to testing any standard fiber cable assembly. If
the system in which a mode conditioning patch cord is correctly installed does
not function properly, simple steps can be taken to rule out the mode
conditioning patch cord as the root cause. Here are the steps.

 

Testing the Multimode/Multimode Leg of
Mode Condition Patch Cord

1. Remove the MCP from the system.

 

2. Reference out a multimode (MM) test
jumper using a 1300nm wavelength multimode source.

 

3. Verify whether the connector on the
receiver (RX) end of the MM reference jumper is good. Connecting the MM
reference jumper to the OTS TX, and connecting another same jumper to another
OTS RX. Then link the two MM fiber jumpers and measure the insertion loss
across the multimode connector pair (just like the following picture shows).
This value should be < 0.5 dB.

 

4. Replace the second MM reference
jumper connected to the OTS RX with a multimode/multimode leg of MCP (shown a
picture below). Measure insertion loss across this multimode connector pair.
This value should be < 0.5 dB too.

 

Testing the Single-Mode/Multimode Leg
of the Mode Conditioning Patch Cord

1. Repeat the same three steps
mentioned above to measure the insertion loss across the single-mode connector
pair (the value < 0.5 dB). The difference is to do it with two single-mode
fiber jumpers.

 

2. Remove the single-mode jumper from
the OTS RX, and then connecting the OTS RX to a MCP cord. Make sure the
single-mode fiber part of the MCP connecting with the single-mode reference
jumper, like the following picture shows. Measure the insertion loss across the
single-mode connector pair.

 

3. Remove the connector of MCP from the
OTS RX, and link the multimode fiber part of the MCP with OTS Rx using a
multimode jumper used in the in the previous section. Showing in the below
picture.

 

 

4. Measure insertion loss. This loss is
the insertion loss of the multimode connector pair. This value should be <
0.5 dB.

 

5. The total insertion loss of the MCP
is the sum of the loss across the two connector pairs. If the insertion loss is
< 1.0 dB, then the MCP cord is functioning properly.

 

If the MCP cord was mistakenly reversed
in the system, then there will be a very high attenuation (on the magnitude of
up to 45.0 dB), which would occur resulting in severely degraded signal
strength.

 

Notes: In the whole testing process, if
the insertion loss is not < 0.5 dB, then you should separate connector pair
and clean them for the second measurement.

 

Conclusion

Mode conditioning patch cable provides
a convenient and reliable method of connecting multimode fiber plants with
1000Base- LX based transmission equipment compliant with IEEE 802.3 standards.
This article introduces a simple method to test mode conditioning patch cable
in network system. Hope it may help you.