Dual-function optical differential phase shift keying format demodulator

Abstract

The invention relates to a dual-function optical differential phase shift keying format demodulator which is used as a DQPSK (Differential Quadrature Reference Phase Shift Keying) demodulator and a DPSK (Differential Phase Shift Keying) demodulator. In the dual-function optical differential phase shift keying format demodulator, an input collimator, a first polarizing beam splitter, a first half wave plate, a quarter wave plate, a second polarizing beam splitter, a second have wave plate, two liquid crystal phase modulation elements, a time-delay crystal, two one-eighth wave plates, a third polarizing beam splitter, a half wave plate group, a fourth polarizing beam splitter and an output collimator are arranged along an optical path. Two liquid crystal phase modulation elements are longitudinally arranged, two one-eighth wave plates are arranged longitudinally, and the half wave plate group is arranged on the same plane both in a longitudinal direction and a horizontal direction. The dual-function optical differential phase shift keying format demodulator has two functions for the upgrading of a DPSK system and a DQPSK system without polarization, avoids the disadvantage of higherrequirements on the film coating technology in a Michelson time-delay interferometer type demodulator, and can be provided with the liquid crystal phase regulation elements in the optical path to realize the function of rapid wavelength regulation.

Description

technical field [0001] The present invention relates to a demodulator. In particular, it relates to a dual-function optical differential phase-shift keying format demodulator which realizes DPSK and DQPSK demodulation in the same device. Background technique [0002] Differential phase-shift keying (Differential phase-shift keying, DPSK) and differential quadrature phase-shift keying (Differential quadrature phase-shift keying, DQPSK) formats can be used in the next generation of high-speed optical transmission systems (40G system and 100G system) modulation pattern. Compared with the intensity modulation format, the biggest advantage of the DPSK modulation format is that the requirements for the optical signal-to-noise ratio are reduced by 3dB when the same bit error rate is achieved (using a balanced detection receiving method); DQPSK is a multi-level differential Phase shift keying format, which represents the transmitted bit information with four phase differences betw...

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Problems solved by technology

But because in the planar waveguide, the light spot is limited to a small area (less than 10um in the lateral direction), so the temperature adjustment only needs to act on this small area, and the response time is often within 50ms

As a comparison, in the free-space optical demodulator, the beam waist diameter after passing through the collimator lens is about 400um, and the temperature adjustment method needs to act on a relatively large area. time is therefore longer

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