In photonic label routing networks, recognition of optical labels is one of the key functions. We have proposed passive waveguide-type devices for recognition of optical labels coded in quadri-phase-shift-keying (QPSK) form. In this paper, we consider wavelength dependence of the devices. The basic module of the proposed device consists of a 3-dB directional coupler, two Y-junctions, and an asymmetric X-junction. The Y-junction and an asymmetric X-junction have basically no wavelength dependence. Although the 3-dB directional coupler has weak wavelength dependence, the device for two-symbol label recognition is found to work in wavelength 1.5-1.6 µm. The performance of the device is confirmed by simulation using beam propagation method (BPM).

We propose a new label recognition system for photonic label switching using self-routing of labels. Binary-coded labels in on-off keying format are considered. The system consists of an all-optical demultiplexer (DeMUX) and an address recognition unit (ARU) consisting of tree-structured switches. The system uses self-routing propagation of an indication bit controlled with address bits. The indication bit is placed in advance of the address bits in the label. In DeMUX, all-optical switches in a configuration of Mach-Zehnder interferometer with semiconductor optical amplifiers (SOA-MZI) are controlled by the indication bit pulse to separate each of the label bits. The indication bit pulse is routed to the destination output port corresponding to the code of the address in ARU. It is shown that all the binary number codes can be recognized with this system. The operation principle is verified by numerical simulation using coupled-mode theory and a rate equation. Moreover, the switching crosstalk is also evaluated.

We propose a new label recognition system for photonic label routing network. Binary-coded labels in binary phase-shift-keying format are considered. The system consists of an optical waveguide circuit with tree-structure passive asymmetric X-junctions and time gates. The system uses self-routing propagation of an identifying bit by performing interference with address bits. The identifying bit is placed in advance of the address bits in the label. The identifying bit pulse is routed to the destination output port corresponding to the code of the address. The operation principle is described. It is shown that all the binary number codes can be recognized with this system. We discuss the feasibility of the system by evaluating its crosstalk. To reduce the crosstalk, an improved scheme is also presented. The label recognition operation with the optical waveguide device is verified by numerical simulation using the finite-difference beam propagation method.