As the demand for higher speed and bandwidth increases, optical modules, which are essential for optical-electrical conversion, have experienced explosive growth. Consequently, optical chips, a crucial component of these modules, have also come into the spotlight.

What is an Optical Chip？

An optical chip, also known as a photonic chip, is an integrated circuit that uses light waves for information transmission and data processing. Typically made from compound semiconductor materials such as InP and GaAs, it achieves optical-electrical signal conversion through the generation and absorption of photons during internal energy level transitions.

These chips rely on dielectric waveguides in integrated optics or silicon photonics to transmit guided light signals. They integrate the modulation, transmission, and demodulation of optical and electrical signals on a single substrate or chip. Compared to traditional electronic chips, photonic chips use light instead of electrical currents to transmit data. This results in high density, high speed, and low power consumption.

In short, optical chips are fundamental components for converting optical signals to electrical signals. Their performance determines the transmission efficiency of optical communication systems.

Development Status of Optical Chip

The development of optical chips dates back to 1969 when Bell Labs in the United States proposed the concept of integrated optics. However, due to technological and commercial challenges, significant progress didn’t occur until the early 21st century. At that time, companies like Intel and IBM, along with academic institutions, began focusing on silicon chip optical signal transmission technology. Their aim was to replace data circuits between chips with optical pathways.

Today, pure photonic devices can function as independent modules. However, they still face limitations. Controlling optical switches is challenging, and these devices can’t act as storage units like electronic devices. As a result, pure photonic devices cannot fully handle information processing on their own and still need electronic devices. Therefore, a purely “photonic chip” is still a concept and not yet a practical system. The current “photonic chips” are actually optoelectronic hybrid chips that integrate photonic devices or functions. They still struggle with integrating high-density light sources and low-loss, high-speed electro-optic modulators.

Despite being in the early stages, photonic integrated circuits are set to become the mainstream in optical device development. The future of photonic chips will involve integration with mature electronic chip technology. Using advanced manufacturing processes and modular techniques from electronic chips, silicon photonics, which combines the strengths of both photonics and electronics, will lead the way forward.

From a market perspective, the United States was the first country to start and excel in the field of silicon photonics. Early on, associations were established to guide capital and various forces into the optoelectronics field. Singapore’s IME is also one of the early platforms for silicon photonics processes, contributing significantly to the industry’s development.

Currently, the global optical chip industry chain has gradually matured, with representative companies involved in every stage from basic research to manufacturing processes and commercial applications. Companies like Intel, Cisco, and NVIDIA dominate the shipment volumes of silicon optical chips and modules, becoming leaders in the industry.

Applications of Optical Chip

High-speed data processing and transmission are the pillars of modern computing systems. Optical chips provide a crucial platform for integrating information transmission and computation, significantly reducing the cost, complexity, and power consumption of connections. As optical chip technology evolves, large cloud computing providers and enterprise customers are transitioning from lower-speed to higher-speed modules. Consequently, optical chips are increasingly being used in high-performance computing and data centers. They are also becoming more prevalent in the telecommunications market.

• High-performance computing

In high-performance computing, optical chips offer high speed and low energy consumption, greatly enhancing computing efficiency and processing speed. This is particularly important for handling large, complex algorithms and models, which are vital in fields such as scientific research, climate modeling, and biotechnology.

• Data center

Data centers are the backbone for data and data processing. The construction of data centers provides the necessary equipment support for large-scale data storage, exchange, and application needs. The larger the data flow, the more complex the data processing methods, making data centers increasingly important. Currently, the global solution to handling data flow is the construction of large-scale data centers. Therefore, the global construction of these large-scale data centers will be a significant driving force for the optical module market, thereby driving the demand for optical chips.

• Telecommunications

Currently, countries around the world are striving to meet the demands of 5G networks. Compared to 4G, 5G uses higher frequencies, which significantly weakens its coverage capability. As a result, the number of base stations required to cover the same area with 5G will undoubtedly exceed that of 4G. The communication services in the 5G era have also created a huge demand for optical chips and optical modules.

Future Trends in Optical Chip

As the internet industry develops, the demand for optical modules is gradually trending towards miniaturization and high performance. The future technological direction of optical chips can be embodied in silicon photonics technology.

Silicon photonics technology is a new generation of technology that develops and integrates optical devices on silicon and silicon-based substrates using CMOS processes. Its core concept is to use laser beams instead of electronic signals for data transmission.

Silicon photonic modules and regular optical modules use different chips, leading to various differences in their product parameters, even at the same speed and in the same scenario.

Since regular optical module technology is more mature and requires lower deployment environment standards, silicon photonic modules will be challenging to scale up in the market in the short term.

Nonetheless, with the further expansion of 5G network construction and the growing demand for data transmission, the silicon photonic module industry is expected to enter a rapid development phase.

Summary

To summarize, optical chips have become a focal point in the industry and one of the most lucrative areas for venture capital. Exploring new technologies has become a key task in the semiconductor field. The application of optical chips will significantly impact the performance of optical modules and has the potential to reshape the existing optical module industry chain.

As the demand for high-performance computing grows, optical modules are evolving to meet these needs. But why choose different optical modules, and how do they function in various situations? This article will delve into the different form factors to help you understand optical modules and explore their close correlation with the number of SerDes channels.

Progression from Fundamental SFP to Advanced OSFP

Optical module consists of optoelectronic devices, functional circuits and optical interfaces, etc. The optoelectronic devices include the transmitter and receiver parts, whose role is to convert the electrical signals into optical signals at the transmitter side, and then convert the optical signals into electrical signals at the receiver side after being transmitted through optical fibers. The form factor of an optical module determines its size and is the primary way to differentiate between optical modules. According to their evolution, optical modules can be mainly divided into nine types, which we will introduce in the following paragraphs.

The Foundation: Small Form-factor Pluggable (SFP)

SFP, or Small Form-factor Pluggable, is a compact, lightweight version of the GBIC module, designed to support gigabit rates. As the successor to GBIC, SFP has become the foundational form factor for modern optical modules.

One of the most significant advantages of SFP over GBIC is its reduced size. The SFP module is half the size of a GBIC module, allowing for more than double the number of ports to be configured on the same panel. This space efficiency is crucial for high-density networking environments.

SFP modules support a maximum bandwidth of up to 4Gbps and are typically equipped with a single gigabit SerDes (Serializer/Deserializer) channel. This capability makes SFP a versatile and widely used option for various networking applications.

Transition to Higher Speeds: SFP+ and SFP28

SFP+, as we can infer from its abbreviation, is a plus version of the SFP module. Its official name is Enhanced Small Form-factor Pluggable. SFP+ is specifically designed for 10Gbps Ethernet, featuring several technical advancements and compatibility with higher speed standards. 

Unlike SFP, which typically supports up to 4Gbps, SFP+ can handle data rates up to 10Gbps, making it a crucial component in modern high-speed networking environments. In addition to the significant increase in data transmission rates, SFP+ retains the compact size and hot-swappable functionality of SFP, allowing for seamless upgrades and maintenance without network downtime. SFP+ modules typically support a single 10Gbps SerDes channel, further enhancing their suitability for high-performance computing and data center applications.

SFP28, short for Small Form-factor Pluggable 28, is an advanced version of the SFP+ module. Although it shares the same size as SFP+, SFP28 supports optical modules with a data rate of 25Gbps. Specifically designed for 25Gbps Ethernet, SFP28 is equipped with a single 28G SerDes channel. SFP28 is essential in modern high-speed networks due to its ability to handle higher data rates while maintaining the compact size and form factor of its predecessors. This compatibility with existing SFP+ slots allows for easy upgrades and integration into current network infrastructures without the need for significant hardware changes.

The introduction of SFP28 addresses the increasing demand for higher bandwidth in data centers, enterprise networks, and other HPC environments. By providing a cost-effective and scalable solution for 25Gbps Ethernet, SFP28 plays a crucial role in the evolution of network technology, ensuring that networks can meet the growing data transmission requirements of today and tomorrow.

Quad Channel Modules: QSFP+ and QSFP28

QSFP+ and QSFP28 are both quad-channel SFP interfaces. Compared to SFP+ optical modules, they are larger in size. The difference between them is that QSFP+ supports 40G, while QSFP28 supports 100G. Specifically, QSFP+ introduces four independent SerDes channels, each supporting 10Gbps, resulting in a total rate of 40Gbps. On the other hand, QSFP28 continues the quad-channel design but increases the rate of each channel to 25Gbps, thereby boosting the total rate to 100Gbps.

Further Enhancements: QSFP56 and QSFP112

QSFP56 and QSFP112 represent advancements in technology with each channel supporting 50Gbps and 100Gbps respectively. QSFP56 offers a total data rate of 200Gbps, while QSFP112 reaches 400Gbps. Both of these modules rely on the same four-channel SerDes technology. However, the significant difference lies in the increased per-channel data rates, allowing for higher overall bandwidth without changing the number of channels. This evolution highlights the ongoing enhancements in optical modules to meet the growing demands for higher data transmission rates in modern high-speed networks.

Exploring Future with QSFP-DD and OSFP

QSFP-DD, or Quad Small Form Factor Pluggable-Double Density, indicates its “Double Density” nature right from its name. This advanced module supports data rates of 200G, 400G, and even up to 800G. With double density achieved through eight channels, QSFP-DD is designed for 400Gbps and beyond. These improvements make it a versatile choice for high-speed networking needs, offering design enhancements that cater to increased bandwidth requirements and various use cases.

On the other hand, OSFP, which stands for Octal Small Form-factor Pluggable, features an octal design, representing eight channels. Slightly larger than QSFP-DD, OSFP modules support 400G, 800G, and up to 1600G data rates. This design not only accommodates higher speeds but also includes considerations for effective thermal management and signal integrity, making OSFP a forward-looking solution for the next generation of high-performance networks.

FS provides newly module catagory of 800G QSFP-DD/OSFP, which paves the way for advancements in optical module technology, addressing the ever-growing demand for higher data rates and efficient performance in modern data centers and network infrastructures.

The Role of SerDes Technology

SerDes, short for Serializer Deserializer, is an electronic circuit commonly used in high-speed communication applications. It converts parallel data into serial data for transmission and then back into parallel data at the receiving end.

From the above introduction, it is evident that the speed and number of SerDes channels are directly related to the speed of optical modules. Simply put, increasing the number of channels or enhancing the speed of individual channels are the two main strategies to boost the total transmission rate of optical modules.

As technology advances, optical modules have evolved from single-channel to multi-channel designs, and SerDes speeds have progressed from 10Gbps to 112Gbps and beyond. Consequently, optical module speeds have upgraded from 1G, 10G, 25G, 40G, 100G, 200G, 400G, to 800G.

The development of SerDes technology not only determines the data transmission rate of networks but also affects the size, power consumption, and cost of optical modules.

Summary

In summary, the evolution of optical module form factors shows trends toward smaller sizes, higher speeds, lower costs, reduced power consumption, long-distance transmission, and hot-swappable capabilities. Increasing the number of channels or the speed of individual channels are the main strategies for boosting optical module speeds. In today’s rapidly advancing information age, the future of optical modules is promising, with ongoing innovations expected to empower high-performance computing and drive further technological progress.