Low Cost Optical Channel Monitors – CTM Series The CTM Series of optical channel monitors is ideal for original equipment manufacturers looking to achieve the necessary cost targets for embedded DWDM monitoring for ROADM, multi-haul and third-party wavelengths applications. These low-cost and ultra-compact optical channel monitors are ideal for use in closed-loop control of power-equalized channels. They offer the capability to monitor DWDM signals with arbitrary modulation formats on a flexible channel grid.

High Resolution Optical Channel Monitor – FOCM Series FOCM01FXC1MN Featuring unprecedented resolution, power and frequency accuracy, the High Resolution Optical Channel Monitor (OCM) by II-VI offers optical spectrum analyzer (OSA) performance in an ultra-compact, cost effective optical networking component. Through proprietary and patented coherent detection and sub-GHz wavelength accuracy, II-VI’s OCM features highly accurate power monitoring of fine spectral slices independent of adjacent channel power and without the need for de-convolution, making it ideal for next generation WDM networks comprised of densely packed super-channel carriers. Coupled with rapid scanning and powerful advanced processing of spectral characteristics, such as valid channel detection, center wavelength and OSNR monitoring, it enables precise network tuning during dynamic network actions and reliable long-term operation. The High Resolution OCM represents the latest addition to II-VI’s industry leading ROADM and wavelength management portfolio, offering unparalleled value to system and network providers through complementary innovations.

https://zhuanlan.zhihu.com/p/92431293

Optical amplification systems involve dynamic control of a variety of components to optimize performance: • Total power adjustment • EDFA gain tilt using attenuators and pump power adjustment • AGC control of pump powers to allow optical channel add/drop • channel power equalization using dynamic optical filters • variable dispersion compensation using FBG technology Depending on the line rate transmitted through the fiber one or more of these control elements are present in the amplifier. A 40Gbps amplifier typically provides concurrent control of all four of these elements. A 10Gbps amplifier may only need to provide total pump power, tilt control and perform some sort of AGC.

EDFA阵列

瞬态控制原理如图2所示，包括前馈部分和反馈部分。前馈环路能够迅速改变泵浦功率，使反转粒子数达到较为适合水平从而有效抑制瞬态过冲/欠冲幅度；反馈环路采用比例积分微分(PID)控制同时补偿放大的自发辐射(ASE)对泵浦功率进行微调，保证稳定时增益误差更低。通过前馈过调算法可以使瞬态性能更好，过调算法的实现依赖于瞬态识别模块的高效、准确判断，在非瞬态过程(一般工作状态)前馈控制输出电流为Kx+B，在瞬态过程时前馈控制输出电流为R(Kx+B)，其中x为输入光功率，K、B为一阶前馈算法系数，R为过调比例。本设计的控制算法灵活在一阶前馈算法无法满足要求时还可采用二阶甚至三阶前馈算法，以达到更好的瞬态抑制效果。

https://fiber.ofweek.com/2014-08/ART-210001-11000-28862877.html

https://www.neophotonics.com/multicast-switch-work-part/

技术专题：波长选择开光（WSS）_光纤在线 - 和我们一起塑造中国光通信的未来！ http://www.c-fol.net/news/content/8/201010/20101011204656.html?btwaf=69795572

基于微机电（MEMs）技术的WSS模块 基于液晶的WSS 除了MEMS和PLC，目前另一类使用较广泛的WSS实现方式是基于液晶技术。这种方案很简单，就像空间光调制器的原理一样，通过将不同波长的光照射在不同的像素上，进而控制相应像素液晶取向，调节光的偏振态改变，再使用检偏器就能控制输出光的强度。 从图16可以看到，系统工作原理和图9所示MEMs-WSS是非常接近的。系统都是通过输入光纤后，再经过一光栅基的波分复用器，将各个波长按空间不同位置解复用开。所不同的是波长选择单元，图9是靠独立的控制反射镜角度来实时改变某个波长的行进方向，以实现任意波长任意路径的上下行。而图16控制光的行进是靠相位变化。液晶的空间光调制器可以根据需要改变某个波长的相位，注意图16中所有光束路线是可逆的。比如所有光波长从图中第一跟光纤输入，通过空间相位调制（SLM），其他N-1个波长改变相位相同，反射回去重新复用后从第二根光纤输出。而需要下行的相位可以改变不一样，则可从第三根光纤输出，相应信号可以传到下行支路。为了更好的理解这个过程，给出了图17的示意图，注意这里简化了波分复用等元件。 之所以这种WSS实现方式近来广受关注，主要是因为该方案灵活性相当高。我们看到MEMs反射镜只改变光的传播方向，而图16的SLM是通过相位改变来调节光路。在相位改变改变光方向的同时，还可以通过相位调节来矫正色散。Optium公司的研究者已经尝试对80Gb/s的高速信号，实现了最多60ps/nm的色散补偿。此外除了补偿色散，我们知道靠调相还可以做很多事情，比如用于脉冲整形等等。因此图16-17所示方案是具有无限衍生功能的WSS，相信未来会受到更多的关注。 我们会发现图16中的SLM使用的是二维LCOS阵列。LCOS是硅基液晶的英文字母缩写。LCOS是近来研究比较火的液晶显示技术之一。 The main advantage of an LCOS switch is that it does not rely on a moving physical component like the MEMS switch, allowing for potentially faster switching, the disadvantage being that this technology limits the direction and resolution of the switch axis to the number of pixels used for each switch area.

基于PLC技术的WSS模块 使用PLC元件制作WSS模块，除了微共振环还有其他一些方法，其中最有代表性的是基于阵列波导光栅（AWG）结构的实现方式。如图15所示的结构是NTT的建议的WSS方案。图示1X4的WSS是由4个AWG和热光相位漂移结构组成的。显然和前面的微共振环一样，是通过热光效应改变相位变化，进而改变不同波长的路由路径。看起来图示结构会比微共振环复杂很多，尺寸也庞大很多。比较有优势的地方是该结构损耗很小，经测试只有平均2.7dB的损耗。