From LCOS to MEMS: How Hirundo’s WSS Achieves Precise Single-Wavelength Routing

Foshan, China - September 11, 2026 - In recent years , large language models, represented by ChatGPT and GPT-4, have ignited a global AI computing power revolution , leading to an epic boom in the optical communication industry. Faced with the rapid growth of AI computing power , traditional electrical switching architectures have encountered three major challenges: power consumption limitations, bandwidth bottlenecks, and latency constraints . Electrical switching can no longer meet the needs of ultra-large-scale data centers. To address these challenges, data centers are beginning to move towards all-optical interconnect architectures , with optical switches being the core components driving this advancement .

Among the many types of optical switches, the WSS (Wavelength Selective Switch) has become an indispensable part of intelligent all-optical switching networks due to its flexible wavelength selection and scheduling capabilities .

What is a WSS optical switch?

WSS optical switches achieve precise selection of optical signal wavelengths through sophisticated optical structures and control mechanisms such as LCOS chips or MEMS . They can distribute any desired wavelength optical signal to any target output port on demand in optical fibers that carry dozens of wavelengths of light, completely breaking through the technical bottlenecks such as bandwidth utilization limitations of traditional wavelength division multiplexers and ordinary optical switches.

Whether using LCOS or MEMS, the basic working logic of WSS is "separate-control-integration" .

1.Demultiplexing:

First, light of different wavelengths is transmitted in the optical fiber. Then, through a diffraction grating or prism, the light of different wavelengths is scattered in space to form a "rainbow".

2.Spatial light processing:

The "rainbow" is focused onto the processing engine (such as an LCOS chip or MEMS micromirror array) through a lens. The engine is responsible for reflecting/deflecting specific colors of light at specific angles. This is the key to the operation of the WSS .

3.Remultiplexing:

The deflected beam passes through the lens and grating again and is recoupled into the corresponding output fiber optic port.

LCOS (Liquid Crystal on Silicon)

LCOS is the most mainstream design scheme for WSS optical switches.

1. Core principle: Phased array

An LCOS chip contains millions of tiny pixels, each of which is a liquid crystal cell. By controlling the voltage applied to each pixel, the alignment of the liquid crystal molecules can be changed, thereby altering the refractive index of that pixel.

The optical path that light travels in a medium is nd (where n is the refractive index of the medium and d is the distance traveled in the medium). By changing the refractive index, the optical path that light travels can be changed, thereby changing the phase of the light before and after passing through a pixel.

2.Now that the phase has changed, how do we turn the steering wheel ?

By using an LCOS chip to deflect the light beam, instead of using a mirror, we use a blazed grating to create a phase gradient . According to physical optics, the propagation direction will also be deflected after the phase changes. We can program the voltage pattern loaded on the LCOS chip to control the reflection angle of the light more controllably and reliably, thereby guiding the light to any output port we want.

Schematic diagram of liquid crystal phase control principle

Schematic diagram of LCOS used for WSS phase change routing principle

3.Advantages of LCOS: No mechanical lifespan, high stability, and good seismic resistance.

It allows for precise bandwidth control, not limited to a fixed frequency interval, and can allocate 37.5GHz or 75GHz channels as needed to adapt to the required signal transmission.Dispersion can be compensated by phase adjustment, and pulse shaping can be performed by phase adjustment to regulate optical power.

MEMS (Micro-Electro-Mechanical Systems)

1. Core Principles

MEMS is a tiny system that combines micromechanical structures, actuators, and electronic control circuits. Its principle is to control the tilt angle of the micromirrors with voltage, thereby changing the propagation direction of the incident light beam and realizing the switching of optical signals between different optical fibers.

For MEMS‑based WSS, once light is split by the grating, different wavelengths hit different micromirrors. The voltage drives the micromirrors to tilt, thereby deflecting the direction of the light.

WSS module using a combination of demultiplexer and MEMS mirror

2.Limitations of MEMS

There are gaps between the micromirrors, resulting in relatively low spectral utilization.

Fixed bandwidth: Each micromirror has a fixed wavelength channel, making it difficult to change flexibly.

Performance indicators

1.Number of ports:

Common configurations include 1x9 , 1x20 , and even 1x32. The more ports a device has, the more directions it can connect to.

2.Insertion loss:

Light inevitably loses energy when passing through gratings, lenses, and liquid crystal/mirrors. The lower the loss of optical devices , the better, as this is beneficial for efficient light transmission.

3.Channel isolation:

Different ports output light of different wavelengths. The light from port A must not leak to port B , otherwise the light will be impure, crosstalk will be high, and the quality of the output light will be poor.

4.Switching speed:

The faster the switching speed of the WSS optical switch, the better its performance. LCOS is typically in the hundreds of milliseconds range, therefore WSS is usually used in intelligent computing centers, all-optical computing, and other scenarios with high requirements for optical channel switching speed, which is crucial for the recovery time of the optical network. Please check the attached Hirundo’s Optical Switch Series:

Q1: What is the core difference between LCOS-WSS and MEMS-WSS from Hirundo?

A: Hirundo’s LCOS-WSS uses phase-modulation of liquid-crystal pixels with zero moving mechanical components; it supports flexible-grid variable bandwidth (37.5 GHz /75 GHz channels), dispersion compensation and fine-granularity spectral shaping. Hirundo’s MEMS-WSS uses electrostatically-tilted micromirror arrays; it delivers competitive insertion-loss performance, suitable for cost-sensitive fixed-grid wavelength-scheduling deployments, though spectral flexibility is limited by fixed-mirror channel mapping.

Q2: What typical port-count options does Hirundo supply for WSS products? Which one fits AI-data-center all-optical interconnection?

A: Standard Hirundo’s WSS covers 1×9, 1×20 and 1×32 configurations. For AI-data-center all-optical-interconnection scenarios requiring multi-direction wavelength routing, 1×20 or 1×32 high-port-count LCOS-WSS are recommended for greater interconnection flexibility.

Q3: What insertion-loss performance can Hirundo WSS achieve? How many WSS devices can be cascaded in one optical link?

A: Hirundo’s WSS typical insertion-loss ranges from 5.5 ~ 7.5 dB(C-band, subject to port configuration). In practical DWDM system design, the number of cascaded WSS stages is generally limited to 2-3 passes to avoid excessive OSNR penalty; optical amplifiers (EDFA/Raman) can compensate insertion-loss when multi-stage cascading is necessary.

Q4: Can Hirundo’s WSS support C+L dual-band operation? What application scenarios benefit most?

A: Custom-version Hirundo’s WSS supports C+L-band coverage. This fits high-capacity 800G/1.6T DWDM transmission, AI-data-center DCI interconnection, and next-generation ROADM network upgrades, effectively doubling available fiber spectrum resources.

Q5: Does Hirundo’s provide SDK or API for WSS remote control? Can it integrate with SDN network-controller systems?

A: Yes. Hirundo’s supplies standard communication interfaces together with SDK / API control libraries for WSS modules. Users can complete wavelength-routing configuration, channel-power adjustment and status-monitoring remotely, supporting docking with mainstream SDN controllers for intelligent automated optical-network orchestration.

Application scenarios

Wavelength selective switches (WSS) are core control devices in the field of optical communication, with core applications revolving around hot areas such as optical transmission, intelligent computing centers, all-optical computing, and communication network upgrades.

1.Intelligent computing centers, which handle large-scale AI model training, massive data storage and scheduling, need to address issues such as insufficient bandwidth and high latency. WSS, with its precise wavelength control capabilities, enables parallel transmission of multi-wavelength signals, significantly increasing fiber optic transmission capacity and overcoming the bandwidth bottleneck of massive data transmission in intelligent computing centers. Furthermore, optical switches can construct unobstructed optical paths, reducing data transmission latency to the microsecond level.

2.5G/6G Communication Networks: 5G/6G communication networks need to support ultra-high-speed data transmission, industrial interconnection, and other scenarios. The core requirements are to increase transmission bandwidth, reduce signal latency, and achieve flexible large-scale signal scheduling, while adapting to the dynamic transmission needs of different scenarios. WSS can achieve rapid switching between different wavelength signals without frequent photoelectric conversion, fundamentally reducing signal transmission latency. Its high spectral utilization characteristics maximize the potential of fiber optic transmission, increase communication network bandwidth, and adapt to the ultra-high-speed transmission requirements of 5G/6G. Simultaneously, it possesses flexible port expansion capabilities, efficiently handling large-scale signal scheduling, meeting the core requirements of 6G's wide connectivity and multi-scenario adaptation, and helping communication networks evolve to a higher level.

3.Spectral analysis and optical sensing: The fields of spectral analysis and optical sensing require the selection of light of specific wavelengths for analysis and measurement. With its ability to quickly switch between different wavelength signals, WSS can respond quickly to the measured spectrum, providing strong support for scientific research, environmental monitoring and medical diagnosis.

About Hirundo

Hirundo has been deeply involved in the field of optical switches for many years , and can create customized optical switch solutions to meet the needs of different scenarios. We can provide mechanical optical switches, MEMS optical switches, WSS optical switches, etc. Our products not only have the advantages of low insertion loss and high reliability, but also meet the needs of high integration and high-speed switching in data centers, as well as adapt to the scorching sun and cold winter of desert photovoltaic power stations, enabling rapid optical path switching and safeguarding various scenarios.

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