Error Detection and Correction

FTTC in Cable TV Network o    Cable TV uses optical fibers to connect and multiplex different cable channels o    Coaxial cables coming from individual premises are multiplexed in the junction box and converted to the optical signals o    Optical signals are multiplexed using WDM at switching office to create wider BW optical signals

ERROR DETECTION AND CORRECTION Introduction o    Networks  must  be  able  to  transfer  data  from  one  device  to  another  with  complete accuracy o    A system that cannot guarantee that the data  received by one device is identical to the data transmitted by another device is essentially useless o    Anytime the data is TX from source to destination, it gets corrupted on the way o    Many factors including NOISE can alter or wipe out one or more bits of a given data unit o    Reliable systems must have a mechanism for detecting and correcting such ERRORS o    Error  detection  and  Correction  is  implemented  either  at  the  data  link  layer  or  at  the Transport layer Types of Errors o    Whenever   an   EM   signal   flows   from   one   point   to   the   other,   it   is   subject   to unpredictable interference from heat, magnetism and other forms of electricity o    This interference can change the shape or timing of the signal o    If  the  signal  is  carrying  encoded  binary  data,  such  changes  can  alter  the  meaning  of the data