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中国物理学会期刊

四波混频光相位运算器原理及其噪声性能研究

CSTR: 32037.14.aps.67.20172638

Principle and noise performance of optical phase arithmetic devices using four wave mixing

CSTR: 32037.14.aps.67.20172638
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  • 推导了抽运消耗情形下简并和非简并四波混频(FWM)闲频光幅度和相位的统一解析表达式.采用极限方法,计算证明了非相敏放大模式下闲频光相位与输入光初始相位之间的关系,揭示了FWM相位加减混合运算器的工作原理.以四相相移键控信号为例,对基于非简并FWM的相位运算器进行了设计,重点分析了三种基本加减混合运算的噪声转移性能及其对光纤长度、输入光波长和功率的依赖特性.计算表明:该运算器的噪声指数约为1.1 dB;当输入光信号的信噪比大于24 dB时无纠错编码的符号错误率可低于10-3.

     

    The existing theoretical equations cannot provide an excellent guidance for developing four-wave mixing (FWM)-based optical logic devices, though the experiments have been done in several researches. The optimization of noise figure performances of such devices should be further investigated. In the paper, the universal analytic expressions for the amplitude and phase of the idler in degenerate or non-degenerate FWM process under pump depletion are derived in detail from the nonlinear coupled-mode equations for guiding optical waves propagation in highly nonlinear fiber. The universal analytic expressions are obtained by the first-and the third-kind of elliptic integrals. By using equivalent infinitesimal to calculate the limit of phase sensitive amplification, we find out the initial phase relationship between the idler and the input guided wave for phase-independent amplification, which is crucially important for explaining the operating principles of the FWM-based adder and subtracter. As an example, the configuration of non-degenerate FWM-based hybrid arithmetic device with three logic functions of A+B-C, A+C-B, and B+C-A for QPSK signals is presented, and then the noise transfer characteristics in terms of signal-to-noise ratio (SNR) and error vector magnitude (EVM) are taken into account by adjusting the fiber length, input wavelength, and optical power. The calculation results show as follows. 1) This kind of arithmetic device has a noise figure of about 1.1 dB and an input SNR of more than 24 dB is necessary for the symbol error rate of 10-3 without forward error correction, corresponding to an output EVM of 23.2%. 2) The length of highly nonlinear fiber used in the hybrid arithmetic device may be taken flexibly, provided that the variation of FWM conversion efficiency is controlled in a range of 1 dB relative to the maximum, with an EVM fluctuation of less than for the idlers. 3) The hybrid arithmetic device has an operating optical bandwidth of about 16 nm for the SNR degradation of 1.3 dB. 4) The output EVM increases with the increase of input power, and the allowable input power should be no more than 100 mW for an input SNR of 28 dB, noting that the larger the input SNR, the higher the allowable input power is.

     

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