Fiber optic transmitter modification for improved extinction ratio

A method of operating laser diode transmitter in an optical data transmission system to increase the signal to noise ratio of the system, comprising the steps of:

• applying sufficient input drive current to said laser diode transmitter so that the output power of the diode changes generally linearly with changes in said input drive current;
• modulating the amplitude of said input drive current to said laser diode transmitter between two distinct input levels to vary the magnitude of the output power of said laser diode between two corresponding distinct output levels;
• selecting a minimum and maximum level of power to be outputted by said system corresponding to said distinct output levels of said laser diode transmitter;
• and
• attenuating said laser diode transmitter distinct output levels to said selected corresponding minimum and maximum levels of system power output using a focusing lens having dopants therein for absorbing a substantial portion of said laser diode output, the level of attenuation provided by said lens being dependent upon the amount of dopant therein.