With the construction of the new generation of intelligent optical network, the demand for ROADM (Reconfigurable Optical Add-Drop Multiplexer), which is composed of WSS (Wavelength Selective Switch) and MCS (Multicast Switch), is increasing rapidly. Aiming at the 1 × N-channel optical switch, which is the core component of MCS, a technical scheme based on optical waveguide array and MEMS micromirror is proposed in this paper. The optical waveguide array with bending transition part is used as the input / output channel instead of the traditional optical fiber array, which can control the crosstalk and greatly reduce the off-axis amount of the edge channel. At the same time, two collimating lenses are used to further reduce the off-axis aberrations of the edge channels to achieve more output channels.
With the vigorous development of data centers, optical fiber interconnection technologies have been evolved from multimode optical fiber (MMF) parallel transmission to CWDM4 single-fiber bidirectional (Bidi) transmission. What’s more, requirements for miniaturization of optical transceivers are put forward. This paper studies a CWDM4 Bidi transceiving module based on hybrid integration technology. Six optical interleavers in serial and parallel connection function as the CWDM4 wavelength division multiplexer and demultiplexer, while an optical circulator is designed with the three inputs/outputs at the same side, which helps to realize Bidi transmission. The former is based on integrated optics and the latter is based on micro-optics. Through the hybrid integration of integrated optics and micro-optics technologies, the transceiving module is minimized and can be integrated into a QSFP module.
This paper reports a wavelength selective switch (WSS) employing a thermally expanded core (TEC) fiber array (FA) as the input/outputs, which enables a compact WSS with convenience for alignment and assembly. Simulation of the WSS module based on ZEMAX shows that conical diffraction of the grating results in horizontal offset of the output beam spots. An excess insertion loss will be caused due to the offset if a linearly aligned FA is employed as the input/outputs. This paper designs a parabolically aligned TEC FA that the fibers in the array can be positioned by V-grooves with different depth. With the parabolically aligned TEC FA as the input/outputs, the WSS module is expected to be compact with low loss.
This paper reports an optical tunable filter array (TFA) based on a LCOS (liquid crystal on silicon) chip. The input broadband optical beam is first dispersed by a bulk grating and then incident on the LCOS chip. The LCOS chip is phase-only modulated and constructed as a dynamic reflective phase grating. The phase modulation is adjusted to meet the Littrow angle for a specified passband wavelength and thus the optical beam corresponding to this wavelength is steered to the output. The input/output optical beams are coupled to optical fibers with a dual-fiber collimator. Four dualfiber collimators are vertically aligned as the inputs/outputs and the pixels of the LCOS chip are vertically allocated as four independent zones. Thus the device can act as a 4-channel TFA, which is assembled and functionally demonstrated.
One of the mini-projects for the course of physical optics is reported. The project is designed to increase comprehension on the basics and applications of polarized light and birefringent crystal. Firstly, the students are required to analyze the basic principle of an optical circulator based on birefringent crystal. Then, they need to consider the engineering optimization problems. The key tasks include analyzing the polarization transforming unit (composed of a half-waveplate and a Faraday rotator) based on Jones matrix, maximizing the walk-off angle between e-ray and o-ray in birefringent crystal, separating e-ray and o-ray symmetrically, employment of a transformed Wollaston prism for input/output coupling of optical beams to fibers. Three years' practice shows that the project is of moderate difficulty, while it covers most of the related knowledge required for the course and helps to train the engineering thinking.