Secure optical communication system
First Claim
1. An interferometric optical communication system, comprising at least one transmitter and at least one receiver connected by an optical channel, the transmitter being provided with an interferometer having an information signal source, a modulator for modulating an output signal of the interferometer, and a pseudo-random signal generator, both the information signal source and the pseudo-random signal generator being connected to the modulator such that the output signal to the optical channel can carry an information signal together with a pseudo-random signal, and the receiver being provided with an interferometer, a demodulator for demodulating an output signal received from the transmitter via the optical channel to obtain the information signal, and a signal generator connected to the demodulator for providing a signal complementary to the pseudo-random signal for use in said demodulation, wherein the pseudo-random signal generated by the pseudo-random signal generator has a greater bandwidth than the bandwidth of the information signal.
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Abstract
A secure optical interferometric communication system and network with multiple access capability where one or more transmitters have an interferometer with phase/Doppler shift difference modulation of spread spectrum type which is used for secure communication with one or more receivers on the optical network where the spread spectrum modulation is known to one or more receivers. The optical source can be of narrow optical spectrum or broad optical spectrum. In the case of the broad optical spectrum source, the path length difference of the transmitting interferometer can be also used to increase the security communication where the path length imbalance is known to one or more receiver, and number of users on the multiple access network. The interferometric communication system, especially with broad spectrum optical sources, can interwork with conventional wavelength division multiplexing (WDM) system and time division multiplexing (TDM) system. The interferometric system can partially tolerate jamming by WDM and TDM systems, and can be made difficult to detect by unintended listener/s.
21 Citations
33 Claims
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1. An interferometric optical communication system, comprising at least one transmitter and at least one receiver connected by an optical channel,
the transmitter being provided with an interferometer having an information signal source, a modulator for modulating an output signal of the interferometer, and a pseudo-random signal generator, both the information signal source and the pseudo-random signal generator being connected to the modulator such that the output signal to the optical channel can carry an information signal together with a pseudo-random signal, and the receiver being provided with an interferometer, a demodulator for demodulating an output signal received from the transmitter via the optical channel to obtain the information signal, and a signal generator connected to the demodulator for providing a signal complementary to the pseudo-random signal for use in said demodulation, wherein the pseudo-random signal generated by the pseudo-random signal generator has a greater bandwidth than the bandwidth of the information signal.
- 15. An optical network for carrying communication signals to or from transmitting/receiving apparatus in optical form, the transmitting/receiving apparatus being adapted to employ interferometric modulation and demodulation as an information-carrying optical communication signal over the network, said interferometric modulation comprising a spectrum spreading signal.
Specification