Communication system and timing control method

Abstract

A communication system and a timing control method are proposed that optimize timing in a sender and thereby enable information to be stably transmitted at the right timing. Under instructions from a timing controller in a receiver, the timing of driving a phase modulator in a sender is shifted by one step after another, and the then amount of clock shift and result of interference are monitored at the receiver and stored in a memory. The optimum timing is determined based on the stored data. Thus, a clock for driving the phase modulator in the sender can be set at the right timing. This is equivalent to compensating for group velocity dispersion due to wavelength dispersion that occurs when an optical signal channel and a clock signal channel are transmitted by wavelength division multiplexing transmission.

Description

technical field [0001] The present invention relates to communication systems, and more particularly to a system and method for determining the timing of operation of a communication device. Background technique [0002] In recent years, in the field of optical communication, research on a quantum key distribution system expected to achieve a high level of security over a transmission link has been actively pursued, and various proposals have been made. [0003] As a basic example, in Bennett and Brassard, "Quantum Cryptography: Public Key Distribution and Coin Tossing," IEEE International Conference on Computers, Systems and Signal Processing, Bangalore, India, pp. 175-179, a method using two bases (base) A system in which quantum encryption keys are shared between a sender and receiver. According to the proposal, the transmitter sends single photons, each photon is phase-modulated with four types of information depending on the combination of two bases (D, R) and two rand...

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Problems solved by technology

This difference in propagation delay between channels is a significant problem for systems that require synchronization of different channel signals

[0019] Also, in a system that uses phase modulation to transmit information, such as the quantum key distribution system described above, it cannot be determined whether the phase modulator drive timing in the transmitter is correct

Therefore, even if the phase modulator is driven with the clock compensated for the propagation delay difference, it cannot be determined whether the compensation result is appropriate without checking the reception result of the receiver

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