Introduction
Butterworth, Chebyshev, and elliptic bandpass filter designs are optimal in terms of passband flatness or equiripple characteristics. This article will introduce the precise optical filter design and simulation of a practically realized microring-assisted MZI, which can accurately and effectively implement the design using ring resonators or reflectors (such as Bragg gratings or thin-film interference filters). The applications of optical bandpass filters include demultiplexing and add/drop functions in wavelength division multiplexing systems. This section demonstrates the implementation of bandpass filters with discrete devices, using ring resonators in silicon-based photonic technology as the fundamental filtering components to accurately realize optimum filter designs.
Link Function Description
A schematic diagram of a passive microring-assisted MZI is shown in Figure 1. For the theory, working principles, and parameter settings of each device in the link, please refer to the tutorial courseware from Shenzhen Free and Unfettered Technology: "SiPh IC Design with pSim" or the Chinese version "Silicon-Based Photonic IC Design - Using pSim". From the output port op_3 of the optical network analyzer (ONA_1), a laser source is used as the light source emitting to the optical attenuator (ATT_1), thereby attenuating the optical power. The PSR is a composite device consisting of a polarization beam splitter and a polarization rotator. Then, the PSR is used to separate the light source into two ports. One port is connected to the terminal (TERM_2). The other port is connected to the straight waveguide (WGD_1). The microring-assisted MZI (my_rmzi_1) is a composite device that needs to be built as an introduced device connecting the left and right ends, consisting of eight microring resonators. The laser source is injected from the op_0 port of my_rmzi_1. The terminal reflector (TERM_1) is connected to the op_1 port of MZI_1, with the reflectivity set to 0.0001 to reflect the optical signal.
Easy Simulation
Using the pLogic schematic editing tool in PIC Studio, you can create schematics, set device and simulation parameters, where device models can come from measurement-based S-parameter data or compact models.
Step 1: Click on Frequency Domain and set all parameters in the Simulation Settings.
Step 2: Create the microring-assisted MZI device (my_rmzi_1). In pSim, users can create their own composite devices and use them in the simulated links.
The internal connections of the device link are shown in Figure 3, consisting of two directional couplers (C_1, C_2), two waveguides (WGD_1 and WGD-2), and eight single-bus microring resonators (RING_1 to RING_1).
Step 3: Select all the devices needed and drag them into the schematic editor window. Set the parameters for each device according to the tutorial courseware "SiPh IC Design with pSim" or the Chinese version "Silicon-Based Photonic IC Design - Using pSim".
Step 4: Connect each device according to the schematic diagram, place probes, and run the simulation. Click on "ONA_1" to display the results. Then right click to open the viewer. The simulation results will be displayed as shown in Figure 4.
Conclusion
Optical filters play a crucial role in modern communications and photonics. Designing and implementing high-performance optical filters is critical for wavelength division multiplexing systems, optical signal processing, and optical communication systems. In this paper, we discussed a new filter design approach where a microring-assisted MZI is introduced as the core component to realize a bandpass filter with highly controllable frequency response. The use of microring resonators allows us to precisely control the frequency response of the filter by adjusting the parameters of the microrings. With the microring-assisted MZI structure, we can effectively meet design requirements and provide highly customizable filter performance.
The pSim photonic IC simulation technology played a key role in this process. With the simulation tool, we can evaluate filter performance, optimize parameters, save time and resources at the design stage, and ensure that the performance of the final product meets expectations.
The microring-assisted MZI structure and pSim photonic IC simulation technology provide us with new tools and methods to realize higher-performance filters, which will play an important role in future communication and photonics applications. We look forward to seeing how these innovations will further advance optical filter technology and provide more solutions for our communication and technological needs.
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