Abstract
Based on cascaded Mach-Zehnder interferometer (MZI) lattice filters, we demonstrate and compare silicon O-band 8-channel (de-)multiplexers with flat and Gaussian-like passbands for the 400 GBASE-LR8 norm. The 1×8 (de-)multiplexer with flat passbands exhibit insertion loss less than 2.5 dB, channel crosstalk lower than −11 dB, and 3 dB bandwidths of ∼3.9 nm. In contrast, the maximum insertion loss, the worst channel crosstalk, and 3 dB bandwidths of the 1×8 (de-)multiplexer with Gaussian-like passbands are 1.1 dB, −13 dB, and ∼2.9 nm, respectively. The comparison result indicates that the latter is more advisable choice. A theoretical calculation based on measured coupling ratios of stand-along directional couplers (DC) indicates that the performance deteriorations of practical filtering curves are mainly caused by dispersions and fabrication errors of the DCs.
Highlights
Driven by exponential growths of data traffics in datacenters, the wavelength division multiplexing (WDM) technology is widely used in various optical interconnect scenarios to increase the data transmission capacity of a single-mode fiber
Silicon photonics is commonly recognized as an enabling technology for optical interconnect thanks to its advantages in CMOS compatibility, high integration density, strong light confinement ability, etc
The insertion loss and the crosstalk can be reduced by using CMOS compatible SiN waveguides with a relatively low refractive index contrast [12], how to actively align passbands with the standard wavelength grids emerges as a tricky issue
Summary
Driven by exponential growths of data traffics in datacenters, the wavelength division multiplexing (WDM) technology is widely used in various optical interconnect scenarios to increase the data transmission capacity of a single-mode fiber. The insertion loss and the crosstalk can be reduced by using CMOS compatible SiN waveguides with a relatively low refractive index contrast [12], how to actively align passbands with the standard wavelength grids emerges as a tricky issue. Compared with the AWG and the PCG, the lattice filter based on the binary tree of cascaded MZIs possesses advantages of low insertion loss, flat transmission passband, and easy tunability. It is known that performances of silicon filters usually deteriorate in O band owing to increased sensitivities of silicon waveguides to sidewall roughness and fabrication errors at short wavelengths. An objective of this work is to develop a silicon lattice-filterbased O-band 8-channel (de-)multiplexer for the 400 GBASELR8 standard. The comparison result suggests that the (de-)multiplexer with Gaussian-like passbands is more suitable for the 400 GBASELR8 standard in view of the present mainstream fabrication precision
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