Re: Equalization
Vipul,
If we assume that DMD can be successfully addressed either through an
appropriate launch and/or DSP techniques then equalization for the
frequency response can be considered a separate issue.
To address your various equalization requirements:
- 5 to 6 dB of equalization gain for 850nm serial links meeting
objective 1 is considered feasible
- 15 dB of equalization gain is also feasible but with some risk
- 22 dB of gain is higher risk
In terms of precedence for this type of equalization:
We currently ship parts for copper cable equalization:
- in hundreds of Mbits range with upto 45 dB of equalization
gain
- in 1.5 Gbps range with upto 30 dB of equalization gain
We have demonstrated copper cable equalization in the 3.2 Gbps range
with about 20 dB of equalization gain.
Hope that helps.
Regards,
Bharat Tailor
Gennum Corporation
Vipul Bhatt wrote:
> Dear colleagues,
>
> I completely agree with Jack's assertion that we don't have much
> time. We should move this discussion along crisply.
>
> We should seriously consider the potential of using a Serial PHY for
> at least 100 meters of installed MMF, preferably 300 meters. In
> principle, there are three ways to attempt it - (A) Enhance the
> effective modal bandwidth of the fiber, or (B) Use equalization
> alone, or (C) use a combination of the two.
>
> (A) alone will not work. No matter how clever a launch technique we
> try, the effective bandwidth of fiber will fall well short of 1
> GHz-Km, even at 1310 nm. We need equalization; question is how much?
>
> (B) and (C) yield interesting possibilities, depending on the amount
> of equalization we agree to attempt. (B) eliminates the need for
> mode launch techniques, while (C) eases the burden on equalization.
> By equalization, I mean to include whatever DSP necessary to
> overcome DMD dynamically.
>
> If we want to try (C):
> ----------------------
> 1. A 1310 nm Serial PMD will take care of P802.3ae Objectives 1 and
> 2 simultaneously. To achieve 8 GHz on 300 meters of 500 MHz-Km
> fiber, we need an equalization gain of 15.6 dB. Is this feasible?
>
> If yes, we may have something truly exciting to talk about. A
> Silicon IC based solution, that supports Objectives 1 and 2 with a
> 1310 Serial PHY - which is already endorsed because it meets
> Objectives 3 and 4? This is too good to be true... so where is the
> catch?
>
> 2. An 850 nm Serial PMD will support Objective 1 with 5 to 6 dB of
> equalization gain. If an equalization gain of around 16 dB is
> feasible, however, it can support 300 meters objective too. The 850
> Serial has the additional benefit of being lower cost.
>
> If we want to try (B):
> ----------------------
> One alternative is to apply the 16 dB gain to 850 nm, unconditioned
> launch, 100 meters installed MMF. This will meet Objective 1.
> Another alternative is to stay with 1310 nm, unconditioned launch.
> This will meet both Objectives 1 and 2 if higher equalization gain -
> about 22 dB - is feasible.
>
> Instead of jumping all over the decision tree, let's first nail this
> down: How many dB of equalization gain is the maximum we should
> attempt, taking into account cost-effectiveness, risk and schedule?
>
> [Footnote: To all the equalization experts on this reflector, I have
> to ask - where have you been? :-) It takes time to build consensus;
> P802.3ae members may find it overwhelming to adopt a new idea at a
> late stage. I urge you to present feasibility of this solution at
> the next meeting, and to start a technical dialog on this reflector,
> quickly, showing proof of feasibility. Speak up now, or forever hold
> your silence...the bride is under pressure to choose the groom!]
>
> Vipul
>
> =================================
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