An optical communication system, having an operating wavelength λ, can use on y % of its source frequency as its channel band width. The system is to be used for transmitting TV signals requiring a bandwidth of N hertz, number of channels can transmit simultaneously, is Cy(2 × z)λN then z is

Optical frequency,  f= Cλ Hz-----(1) Band width of channel (y% of source) = y100f=yC100λ from (1)  Band width needed per channel = N   ∴ Number of channels =Total bandwidth of channelBandwidth needed per channel                                            ==yC100λN=yC100λN        According to given data  :       yC100λN=Cy(2 × z)λN         ⇒   2×z=100         ⇒z=50