RE: Equalization
A B S O L U T E L Y ! ! !
jt
>-----Original Message-----
>From: Vipul Bhatt [mailto:vipul.bhatt@xxxxxxxxxxx]
>Sent: Tuesday, July 18, 2000 6:57 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
>cord.
>
>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.
>
>Thanks,
>Vipul
>
>vipul.bhatt@xxxxxxxxxxx
>(408)542-4113
>