Proposal of all-optical wavelength-selective switching using waveguide-type Raman amplifiers and 3-dB couplers

Design of a variable optical attenuator with wavelength selectivity

“…However, we observe that the switches proposed in [2] only amplify the wavelengths routed to one of two output ports, and do not amplify the wavelengths routed to the other one. This property may induce large power differences among the wavelengths of the switches.…”

“…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.…”

“…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].…”

“…Therefore, the objective of this paper is to design a VOA with wavelength-selective capability and fast operational speed so that it can smoothly cooperate with the similar switch as described in [2,3] or [4]. Because our design is basically following the switch structure proposed in [2], where many important issues for the accurate simulation and implementation have been discussed, we will focus our effort to theoretical analyzes for our VOA proposal.…”