Will a low light level on a receiver in the headend and/or node cause noise related problems with upstream and downstream channels in an HFC network? If so, what type of problems and/or recommendations do you suggest to fix the problem?
Thanks
Will a low light level on a receiver in the headend and/or node cause noise related problems with upstream and downstream channels in an HFC network? If so, what type of problems and/or recommendations do you suggest to fix the problem?
Thanks
What level of light do you have coming into the receiver?
We have .2 and .3 of dc voltage of light measured at the receiver. Anything above the .3 mark and the low light indicator goes off. Is there an optimal range, where even though the indicator is not on, we should be in because of signal degradation? Most of our nodes have a light level from .2 to .5 with one at 1.2 dc volts at the receiver. Also, can I assume if we double the light going to a particular node, we also double the voltage. I would not want to burn up the receiver because I assumed wrong. Thanks!
You have to know what is the optical input power range of the receiver.
Remember that SNR below that range is low, eg:
for +2 dBm optical power - SNR = 55 dB,
for -8 dBm optical power - SNR = 44 dB
or actually lower, depends of number of amplifiers, RF level, etc.
http://www.emcore.com/wp-content/themes/emcore/pdf/Model-2809.pdf
Darek
In our case we read light in dB. It wouldn't be a bad idea if your dealing with fiber to invest in a cheap light meter. You can find a few on ebay for around $100 or so. Some node receivers maybe different but our (Cisco GainMaker Node) like getting hit with -3dB to +2dB. We strive to hit each node at 0dB. Changing light level will increase your RF out of the laser.