Novel Wavelength Multiplexer Using (N + 1) × (N + 1) Arrayed Waveguide Grating and Polarization-Combiner-Rotator on SOI Platform

We propose an ultra-compact novel wavelength multiplexer employing a (
N +
1) × (
N +
1) arrayed waveguide grating (AWG) and a polarization-combiner-rotator (PCR) on the SOI platform, to realize a multiplexing for 2
N
wavelengths with a spacing of Δλ. The (
N +
1) × (
N +
1) AWG works at a bidirectional way to provide two groups of
N
 × 1 wavelength multiplexing with each group having a channel spacing of 2×Δλ, and the central wavelengths of all input channels in one group have a wavelength shift of Δλ with respect to those in the other group. The double channel spacing results in a significant decrease on the footprint of the (
N +
1) × (
N +
1) AWG-based multiplexer compared with a conventional 2
N
 × 1 AWG multiplexer with the same wavelength spacing Δλ. Due to the fact that a single mode fiber is insensitive to the polarization of input light, if we consider short reach datacom applications such as 100/400 GbE, the two separate multiplexing outputs of the (
N + 
1) × (
N + 
1) AWG can be combined as one output with one half wavelengths working at TE polarization and the other at TM polarization by employing a low loss and broadband PCR. In the experiment, we demonstrate a 16 × 200 GHz multiplexer based on a 9 × 9 AWG. The experimental results show that the on-chip loss of the fabricated multiplexer is 2.7 dB and the loss uniformity is 0.5 dB. The 1-dB and 3-dB bandwidths are >0.56 nm (i.e., 35% of the wavelength spacing) and >1.1 nm (i.e., 69% of the wavelength spacing), respectively. They can also be further increased by decreasing the gap between adjacent input waveguides at the interfaces of star couplers of the designed AWG without inducing an excess loss. The proposed multiplexer has great potential for application to future super large capacity (> Tb/s) data transmission systems.