Optical transmission system with receiver using full optical clock recovery

在一种光传输系统中，发射机(2)产生一个时分多路复用脉冲序列，通过光传输媒体(4)发送给接收机(6)。在接收机(6)中，所接收的光多路复用信号加到光多路分路器(30)和时钟恢复装置(48)上。时钟恢复装置(48)产生光时钟脉冲，用来控制光控光开关(32，...，38)，对光信号进行多路分路。光时钟恢复电路基于由所接收的光信号加以模式锁定的激光器。模式锁定激光器包括一个光放大器(50)，它的输出端由包括极化控制器(52)、饱和吸收器(61)、耦合器(56)和可调延迟器(51)的反馈回路接至它的输入端。饱和吸收器(61)包括与一个次级回路连接的3dB、90°耦合器(54)。所述次级回路包括衰减器(60)和放大器(62)。放大器(62)不对称地配置在次级回路内。由于次级回路内的非线性，在次级回路内传播的光脉冲在信号电平低时相消干涉，而在信号电平高时相助干涉。 In an optical transmission system a transmitter (2) generates a sequence of time domain division multiplexed pulses and transmits them via an optical transmission medium (4) to a receiver (6). In the receiver (6) the received optical multiplex signal is applied to an optical demultiplexer (30) and to a clock recovery element (48). The clock recovery element (48) generates optical clock pulses which are used to control optically controlled optical switches (32 . . . 38) which demultiplex the optical signal. The optical clock recovery circuit is based on a laser which is mode locked by the received optical signal. The mode locked laser comprises an optical amplifier (50) having its output coupled to its input by a feedback loop comprising a polarization controller (52), a saturable absorber (61), a coupling element (56) and a adjustable delay (51). The received optical signal is coupled into the feedback loop by means of the coupling element (56). The saturable absorber (61) comprises a 3 dB, 90° coupling element (54) being coupled to a secondary loop. Said secondary loop comprises an attenuator (60) and an amplifier (62). The amplifier (62) is placed asymmetrically in the secondary loop. Due to the non-linearity in the secondary loop, the optical pulses propagating in the secondary loop interfere destructively for low signal levels, and interfere constructively for high signal levels.