Optical-connection direct-light modulation information transmission system with a passband extended towards the low frequencies and continuous waves

Claim 1

A direct-light modulation information transmission system comprising: optical emission means having an output emitting diode for converting electrical signals to be transmitted into optical signals by direct modulation; an optical connection for transmission of the said optical signals; optical receiver means having an input photodiode for converting conversely said transmitted optical signals into electrical signals; and means to prevent signal deformations which may result from temperature junction of said respective diodes, so as to extend the passband of the system to low frequencies and continuous waves, said means comprising: first filtering means for avoiding non-linear thermal effects from said diodes, said first filtering means comprising high-pass filter means, coupled to said emission means, for reducing the level of said electrical signals whose frequency is lower than a predetermined low-frequency value, and first low-pass filter means, coupled to said receiver means, and having a reverse transfer function of said high-pass filter, for reestablishing the level of said low frequency electrical signals, and second filtering means for compensating linear thermal effects from said diodes, said second filtering means comprising at least one second low-pass filter means, coupled to said receiver means, for compensating the linear thermal effects produced by said emitting diode on low-frequency electrical signals passing through said high-pass filter.