clock revery of serial data

[dineshbhutani@yahoo.com]

Dear Friends
i m working on a project --"digitized voice transmission over optical fibers". finding difficulty in recovery of clock & synchronisation at receiver..pls suggest some idea...for details please mail at "dineshbhutani@yahoo.com"
thanks

 

[Nigel Goodwin]

Try googling for "manchester coding".

 

[StopGo]

Also investigate NRZI encoding, and bit stuffing.

Clock recovery usually means some kind of PLL (phase locked loop)

 

[poopeater]

Also investigate NRZI encoding, and bit stuffing.

Clock recovery usually means some kind of PLL (phase locked loop)

I second this. For my senior project, we did a fiber optic data link. We ended up going with NRZI encoding for our bitstream. There was an ASIC at the receiver end that took care of the clock extraction and data retiming.

Modern high speed interfaces use NRZI encoding (for USB) and 8B/10B encoding (for PCI-Express, SATA, SAS, etc)

 

[dineshbhutani@yahoo.com]

Thanks.
pls also convey whether the ASIC was specially designed for your project or a general purpose for clock recovery..pls mention the no.
Also pls suggest how to convert a ttl multiplexed data into NRZ coding'

I second this. For my senior project, we did a fiber optic data link. We ended up going with NRZI encoding for our bitstream. There was an ASIC at the receiver end that took care of the clock extraction and data retiming.

Modern high speed interfaces use NRZI encoding (for USB) and 8B/10B encoding (for PCI-Express, SATA, SAS, etc)

 

[poopeater]

Thanks.
pls also convey whether the ASIC was specially designed for your project or a general purpose for clock recovery..pls mention the no.
Also pls suggest how to convert a ttl multiplexed data into NRZ coding'

The ASIC was a standard off the shelf part. I did the project over 6 years ago, and do not remember the part #.

For the NRZI data stream, I wrote my own NRZI encoder, packet framer, and serializer using an Altera branded programmable logic device.

 

[StopGo]

what do you mean by "ttl multiplexed data" ?

 

[dineshbhutani@yahoo.com]

TTL Multiplexd data means " digitaly encoded multiple channnels multiplexed in time domain --with frames & sysnchronisation e.g E1 or T1 Carrier system....& TTL is Transistor Transistor Logic...0V & 5v working voltage"..
Pls guide how to write the encoder. Thanks

 

[hjames]

Look for communication chips - there is a category of chips called "serializer" / "deserializer" chips which take a lot of parallel data in, collapse it into a higher frequency serial data stream for compression, and then pull it back out.

fer instance:
**broken link removed**
(or just search for serializer on their site)

or

**broken link removed**
[and it's corresponding serializer]
**broken link removed**

If you really want to mess with things, grab an ethernet PHY chip, or SDI interface chip and replace the wire with the fiber optics.

James

 

[poopeater]

TTL Multiplexd data means " digitaly encoded multiple channnels multiplexed in time domain --with frames & sysnchronisation e.g E1 or T1 Carrier system....& TTL is Transistor Transistor Logic...0V & 5v working voltage"..
Pls guide how to write the encoder. Thanks

I just researched around until I found a copy of a spec on NRZI encoding. Then, using the specification, I wrote my own packet framer and encoder using AHDL.