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1.PMD(Polarisation Mode Dispersion)偏振模式色散偏振模式色散是由光纤的随机性双折射引起的,即不同极化状态下光纤的折射率不同,从而导致相移不同,在时域上表现为不同极化态之间的群时延不同,最终使脉冲波形发生展宽,增加了码间干扰,其产生机制是由于制造过程产生的纤芯的椭圆度和非对称机械热应力以及外部弯曲或扭曲影响.因而由偏振模式色散引起的码间干扰可以等效为功率代价,应该包括在允许通路代价中.发送机和接收机应能够容忍0.3 bit周期的微分群时延.实际系统的微分群时延是一个随机的参数,极化模色散不是一种稳态现象,而是随周围温度和压力条件而统计变化的,与光纤或光缆的性质有很大关系.
1. PMD (Polarisation Mode Dispersion) Polarization Mode Dispersion Polarization Mode Dispersion is caused by the random birefringence of the fiber, that is, the refractive index of the fiber is different in different polarization states, resulting in different phase shifts and different in the time domain The group delay between polarization states is different, which finally broadens the pulse waveform and increases intersymbol interference. The mechanism is due to the ellipticity and asymmetric mechanical thermal stress of the core and the external bending or distortion caused by the manufacturing process . Therefore, intersymbol interference due to polarization mode dispersion can be equivalent to the power penalty and should be included in the permissible path cost. The transmitter and receiver should be able to tolerate 0.3 bit periodic differential group delay. The actual system differential group delay Is a random parameter. Polarization mode dispersion is not a steady-state phenomenon, but changes statically with the ambient temperature and pressure conditions, and has a great relationship with the properties of the optical fiber or optical cable.