I definitely think it is worth discussing. We still have unmet objectives
and anything that will help build consensus around viable solutions is a
step in the right direction.
> -----Original Message-----
> From: Vipul Bhatt [mailto:vipul.bhatt@xxxxxxxxxxx]
> Sent: Tuesday, July 18, 2000 8:57 PM
> To: stds-802-3-hssg@xxxxxxxx
> Subject: Equalization
> Dear colleagues,
> As we think about 10G on installed MMF, there is one issue we
> haven't discussed - equalization. Perhaps thinking about it will
> throw more light and provide another perspective.
> In theory at least, equalization looks very promising. Even at 850
> nm, it can permit a Serial PHY to operate over 100 meters on
> installed MMF, or a WWDM PHY to operate over 300 meters on installed
> MMF. At 1310 nm, longer distances can be achieved. (Ignoring DMD for
> the moment, and using a linear system single pole approximation, a
> 20 dB equalization gain will make a 100 meter segment of installed
> MMF look like a 16 GHz channel at 850 nm.) It can be cost
> effective - a single BiCMOS chip with DSP on CMOS, and receiver
> preamplifier in SiGe. It may even eliminate the mode conditioning
> patch cord.
> In reality, there are a couple of challenges, applicable to both 850
> nm and 1310 nm cases.
> 1. DMD: Can equalization overcome DMD? Some have suggested that DMD
> can be modeled as a multipath effect, something that the folks in
> wireless industry know how to deal with. When viewed in terms of a
> transversal filter, the multipath problem boils down to having
> enough taps and setting their coefficients. And if we can undo the
> DMD effect with an IC, we can eliminate the mode conditioning patch
> 2. Initialization: After power on, are a few milliseconds of
> randomized A/K/R enough to initialize the equalizer? Can we assume
> that equalizer will not need to be re-calibrated after that? We
> don't want the tail wagging the dog - equalization should not
> require complex Auto Negotiation.
> Though new to fiber optics, electrical equalization is a
> tried-and-proven concept. We will see more of it as our hunger for
> bandwidth continues to outpace our ability to replace installed
> low-bandwidth media. Fiber optic folks had the luxury of ignoring it
> because fiber bandwidth was plentiful - until now.
> I am asking if this idea is worth discussing.