Scatmag.com

April 2013

DISH DOCTOR
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1310 & EDFA

Q: My subscriber number is 13155. I visited the SCaT exhibition in November and saw many useful products.

I need to buy a converter for a 1310nm transmitter to be used with a 1550nm EDFA, so that I can feed the 1310nm signal to the EDFA.

Thanking you.

A.Chandrasekhar Rao, By Email.

ANS: It is nice to know that you found the SCaT 2012 show useful.

1. It is theoretically possible to optically convert a signal from 1310nm to 1550nm. However, I am not aware of any direct optical converter available commercially for cable TV applications.



2. An optical input of 1550nm can be created for the EDFA from 1310nm as follows (also see the diagram):

i. The 1310nm optical signal is fed to an optical node.

ii. The output of the optical node is an RF output which is fed to the input of a 1550nm optical transmitter. Do note that 1550 NM optical transmitters are expensive and usually available only from large hardware distributors in metro cities. You can select a 1550nm optical transmitter with low output of 6dBm max since the EDFA requires an input of 6dBm max.

iii. The output from the 1550nm optical transmitter directly feeds your EDFA. The EDFA output would usually feed an optical splitter to get 4 or 8 optical trunk outputs. Please also refer to the January 2013 Dish Doctor section for additional info on EDFA use.

Since the 1550nm optical signal is planned to be used with EDFA optical amplifiers it is best that the 1550nm transmitter be an externally modulated transmitter. This will enable upto 17dBm to be launched into each long (trunk) fiber. If you do not use an externally modulated 1550nm optical transmitter, you will only be able to launch 13.5 dBm into each long (trunk) line. Of course, 1550nm externally modulated transmitters are much more expensive but necessary if you plan to optimally use your EDFA system.


Dish Doctor
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