Laser diode optical modulating devices

An optical isolator for transmitting a forward light beam from an input to an output and for blocking a reverse light beam from passing from the output to the input, comprising:

• a first channel and a second channel coupled in parallel between the input and the output, each channel comprising
• first electronically controllable optical switching means coupled to said isolator input;
• second electronically controllable optical switching means coupled to said isolator output;
• means for optical coupling between said first switching means and said second switching means and having an associated delay T.sub.0 ;
• and
• means for providing a first square wave actuation signal to said first switching means and for providing a second square wave actuation signal to said second switching means, said first and second square wave signals each having a cycle time T.sub.p =4T.sub.0 and said second square wave signal being delayed relative to said first square wave signal by a time T.sub.0 ;
• and
• synchronizing means for providing said square wave signals to the respective first switching means of said first and second channels with a phase difference of one half cycle time T.sub.p /2, whereby said forward light beam is continuously transmitted between said input and said output.

A modulated optical source for providing a light beam modulated by a digital modulation signal comprising:

• source means for generating the light beam;
• and
• a unidirectional optical modulator having an input for receiving said light beam from said source means, and an output, said modulator comprising
• a first channel including a first electronically controllable optical switching means coupled to said modulator input, a second electronically controllable optical switching means coupled to said modulator output and first coupling means for optical coupling between said first and second switching means and having an associated delay T.sub.0,
• a second channel coupled in parallel with said first channel between said modulator input and output and including a third electronically controllable optical switching means coupled to said modulator input, a fourth electronically controllable optical switching means coupled to said modulator output and second coupling means for optical coupling between said third and fourth switching means and having an associated delay T.sub.0,
• means for providing a first square wave signal to said first switching means, a second square wave signal to said second switching means, a third square wave signal to said third switching means, and a fourth square wave signal to said fourth switching means, said square wave signals each having a cycle time T.sub.p =4T.sub.0, said third square wave signal being delayed relative to said first square wave signal by one half cycle time T.sub.p /2 and said second and fourth square wave signals being delayed relative to said first and third square wave signals, respectively, by T.sub.0, and
• means for gating said digital modulation signal with said first square wave signal and with said third square wave signal so that said first switching means is on only when said digital modulation signal and said first square wave signal are active and said third switching means is on only when said digital modulation signal and said third square wave signal are active.