Optical Signal Processing by Phase Modulation and Subsequent Spectral Filtering Aiming at Applications to Ultrafast Optical Communication Systems
Optical Signal Processing by Phase Modulation and Subsequent Spectral Filtering Aiming at Applications to Ultrafast Optical Communication Systems
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DOI：
10.1109/jstqe.2008.920293
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发表时间：
2008-06
影响因子：
4.9
通讯作者：
K. Igarashi;K. Kikuchi
中科院分区：
文献类型：
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作者：
K. Igarashi;K. Kikuchi
本文介绍了基于光相位调制和随后的光滤波的光信号处理，这是适用于160-Gb/s的光时分复用（OTDM）子系统。当光脉冲通过非线性光纤时，通过自相位调制（SPM）和交叉相位调制（XPM）来实现光信号的超快相位调制。这种相位调制引起光信号的光谱偏移。各种类型的光信号处理可以简单地通过滤除光谱偏移分量来实现。使用SPM为基础的脉冲整形在一个500米长的二氧化硅为基础的高度非线性光纤（HNLF），我们展示了高度稳定的产生10 GHz的2 ps的光脉冲序列可调在整个C波段。锁相环（PLL）可以抑制由非线性光纤长度波动引起的输出脉冲序列的缓慢相位漂移，使得脉冲发生器能够应用于160-Gb/s OTDM发射机。基于2 m长光子晶体光纤中的交叉相位调制，实现了160 Gb/s光信号的光时分解复用。与由传统的基于二氧化硅的HNLF构成的器件相比，长期稳定性显著提高，因为短的光纤长度减少了信号脉冲和控制脉冲之间的相位波动。代替非线性光纤，诸如（LN）调制器的电光调制器也以更实用的方式执行相位调制。我们提出并证明了一个光电时分解复用方案的160 Gb/s的OTDM信号，其中包括一个LN相位调制器驱动的40 GHz的电时钟和光学带通滤波器（BPF）。我们还演示了从160 Gb/s的光信号与光电PLL的基时钟恢复。相位比较器仅由LN相位调制器和光学带通滤波器组成，保证了160 Gb/s接收机的稳定可靠工作。
This paper describes optical signal processing based on optical phase modulation and subsequent optical filtering, which is applicable to 160-Gb/s optical time-division multiplexed (OTDM) subsystems. Ultrafast phase modulation of an optical signal is done by self-phase modulation (SPM) and cross-phase modulation (XPM) when an optical pulse passes through a nonlinear optical fiber. Such phase modulation induces the spectral shift of the optical signal. Various types of optical signal processing are realized simply by filtering out the spectral-shifted component. Using SPM-based pulse reshaping in a 500-m-long silica-based highly nonlinear fiber (HNLF), we demonstrate highly stable generation of a 10-GHz 2-ps optical pulse train tunable over the entire C band. A phase-locked loop (PLL) can suppress the slow phase drift of the output pulse train induced by fluctuations of the nonlinear fiber length, enabling the application of the pulse generator to a 160-Gb/s OTDM transmitter. Based on XPM in a 2-m-long photonic crystal fiber, optical time-division demultiplexing of 160-Gb/s optical signals is demonstrated. The long-term stability is drastically improved as compared with the device composed of a conventional silica-based HNLF, because the short fiber length reduces the phase fluctuation between the signal and control pulses. Instead of nonlinear fibers, an electrooptic modulator such as a (LN) modulator also performs the phase modulation in a more practical manner. We propose and demonstrate an optoelectronic time-division demultiplexing scheme for a 160-Gb/s OTDM signal, which consists of an LN phase modulator driven by a 40-GHz electrical clock and an optical bandpass filter (BPF). We also demonstrate base-clock recovery from a 160-Gb/s optical signal with an optoelectronic PLL. The phase comparator is simply composed of an LN phase modulator and an optical BPF, ensuring the stable and reliable operation in the 160-Gb/s receiver.