Fiber Communications IP

Does your system have multiple converters?  Having trouble communicating between converters with the latency you require?   Having issues with common-mode noise disrupting your communications?  Reliability not good enough?  ELMG has the product for you.

ELMG fiber communications IP is a FPGA IP block which sends a self-clocking serial packet data stream down plastic optical fiber at rates of up to 40Mbps.  With a customizable message packet both latency critical data and non-critical data can be sent over the stream from one unit to many controllers in a point to multipoint arrangement.  ELMG’s solution also provides synchronization through PLLs to ensure that all converters are all in-sync.

How Does It Work

ELMG’s fiber communications works by first encoding your message data into 8b10 codes.  Use of these codes allows special codes for message framing, synchronization and clocking.  Using a finite state machine, the message packet is formed.  Following the header the latency-critical encoded data is sent followed by its CRC.  This allows the latency-critical data to be used by the receiver immediately after it is checked for errors.  Synchronization codes follow and then the message ends with the latency-non-critical data and it’s CRC.   This system uses error-detection but can be customized to use error-correction at the expense of latency.

Benefits of the IP

One of the key benefits of this IP is the ability to send data long distances (up to 300m, dependent on choices of fiber optics) using noise immune fiber optic systems.  This can be very important in large power converter systems which fill the environment with disruptive common-mode noise during switching.  It also allows you to reduce costs by reducing the number of fibers to one-per-direction as the clock and data are multiplexed.  Further benefits allow customization of the message packet to allow you to help determine the tradeoffs between throughput and latency that are fixed in other systems.

Additional Services

As well as assisting you in customizing your IP, ELMG can help with your choices of fiber optics and partitioning your data into latency-critical and latency non-critical components.  Reducing the amount of latency-critical data reduces the latency and/or the cost of your fiber optics by reducing throughput.  ELMG can also assist in analysis of your control loop to determine the maximum latency that is tolerable before your control loop is too adversely affected.

Download the datasheet here