Low-Complexity and High-Flexibility Design of a Wavelength-Selective Switch Using Raman Amplifiers and Directional Couplers

Design of a variable optical attenuator with wavelength selectivity

“…Recently, a kind of high-speed wavelength-selective switch constructed with several waveguide-type Raman amplifiers and waveguide-type direction couplers has been proposed [2][3][4]. By properly pumping injection wavelengths to the Raman amplifiers in the switches, the corresponding wavelengths multiplexed in the incident WDM signal will obtain power amplification and will be selectively routed to a particular output port.…”

“…This property may induce large power differences among the wavelengths of the switches. The switches in articles [3] and [4] improve the power gain property to be configurable, however, the power gain for the wavelengths in the switches may be still unequal. For instance, the configurable power gains of the wavelengths switched to output port 2 must be greater than 10.79 dB; whereas the power gains of the wavelengths switched to output port 1 are bounded lower than 6.02 dB for the least complexity switching structure of the 1 × 2 switch in [3].…”

“…The switches in articles [3] and [4] improve the power gain property to be configurable, however, the power gain for the wavelengths in the switches may be still unequal. For instance, the configurable power gains of the wavelengths switched to output port 2 must be greater than 10.79 dB; whereas the power gains of the wavelengths switched to output port 1 are bounded lower than 6.02 dB for the least complexity switching structure of the 1 × 2 switch in [3]. Similarly, when a 2 × 2 switch described in [4] is working in the bar state, the configurable power gains of the selected wavelengths must, respectively, be greater than 15.31 and 42.53 dB for the two output ports of the switch; whereas, when the 2 × 2 switch is working in the cross state, the power gains of the unselected wavelengths for both output ports are 0 dB [4].…”

“…In addition, for a large-scale optical switch that is constructed using these switches in [2][3][4], every wavelength needs to undergo many units of these switches with different combinations of power gain. As a result, the accumulated gain differences among the wavelengths at the output port of the large-scale WDM switch are very large.…”

“…To avoid the requirements of demultiplexing and re-multiplexing, some kinds of tunable filters are also considered to perform dynamic equalization such as tunable fiber Bragg gratings [9], or acousto-optics [10]. However, their operational speeds are not fast enough to be compatible with the switches in [2][3][4].…”