Re: [8023-10GEPON] [POWER_BUDGET] Min code gain requirement
Dear All,
Until now, it seems to me that almost all discussions on FEC concentrate
only on how to match with the MAC rate, line rate etc. There are very
little discussions on FEC to help the design to fulfill the system power
budget.
Is it possible for the power budget ad hoc group to define a minimum
required coding gain of FEC, say 4dB optical gain or ~6dB electrical gain.
(RS(255,239) can achieve almost 6dB electrical code gain at BER=1e-12 and so
we may define the minimum coding gain based on this reference.) After
defining the minimum value of code gain, it become possible to examine the
maximum code rate, minimum code length and FEC algorithm all together to
achieve the target code gain. With this kind of figures (max. code rate,
min code length, etc), we can then go back to examine whether it is possible
to do with the MAC and line rates. If it is possible, then we can go ahead,
otherwise we can feedback that the required min code gain is not a feasible
requirement.
FEC, which is the most flexible module in the system, allows us to make any
change on its parameters easily compared with other optical device. We can
adjust the code rate and code length to obtain difference coding gain (with
penalty on the bandwidth efficiency and complexity). Unlike other optical
devices, FEC no need to wait for the technology improvement to achieve a
better gain.
If we need a high power budget to achieve a higher split ratio (say 64,
128бн), FEC is a good choice to solve this problem.
Regards,
Raymond