Analysis of the Current Coherent Optical Module Market

Researchers have made great progress in optical devices. The output power of laser, linewidth, stability and noise, as well as the bandwidth of photodetectors, power capacity and common mode rejection ratio have been greatly improved. Microwave electronic devices have also been greatly improved. Then, the coherent optical communication technology has gradually become an important capacity-lifting solution for the current 100G line-side.

Market Demand for Coherent Optical Communication

One of the biggest drivers of growth in the current communications market is the transition from 10G to 100G in the metro, core and Data Center Interconnect (DCI) sectors.

With the explosive growth of information generated by the use of communication technologies such as video conferencing and the spread of the Internet, the market has proposed higher transmission performance requirements for the physical layer that is the basis of the entire communication system.

OSNR: 16QAM vs. 64QAM

In terms of digital communication, how to expand the capacity of C-band amplifiers, overcome the deterioration of fiber dispersion effects, and increase the capacity and range of free-space transmission have become important considerations for researchers; in analog communication, sensitivity and dynamic range are key parameters of systems.

Driven by strong demand, large-scale DWDM systems are gradually depleting their wavelength resources, and the efficiency of Time-Division Multiplexing (TDM) systems through compressed optical pulses also has a large technical bottleneck. People began to consider replacing the original Wavelength Division Multiplexing (WDM) system with a coherent optical communication system.

Advantages of Coherent Optical Modules

The coherent optical communication system modulates the signal to the optical carrier by adjusting the amplitude, phase and frequency by means of external light modulation (such as DP-QPSK) at the transmitting end.

Compared with the traditional direct detection system, coherent detection can obtain more signal information through the signal light and the beat frequency of the local oscillator; after the signal reaches the receiving end, it uses high-speed Digital Signal Processing (DSP) technology to perform front-end processing such as equalization. The optical mixer and the optical signal generated by the local oscillator are coherently mixed to realize signal reconstruction and distortion compensation.

Baud rates: QPSK vs. DP-QPSK

Coherent optics can be used in both 100G and 400G applications, primarily because it enables service providers to send more data over existing fiber, reducing the cost and complexity of network upgrades for bandwidth expansion.

  1. Coherent detection combined with DSP technology:
    • Cleared barriers to traditional coherent reception
    • Compensate for various transmission impairments in the electrical domain, simplifying transmission links
    • Make high-order modulation formats and polarization states possible
  2. At the same time, the application of high-order modulation formats enables coherent optical communication to have higher single-wavelength channel spectrum utilization compared to traditional system systems.
    Coherent receivers have no special requirements for fiber channel, so coherent optical communication can use already laid fiber lines. With the aid of digital signal processing algorithms, coherent receivers compensate for signal distortion caused by fiber dispersion, polarization mode dispersion, and carrier phase noise at a very small cost.
  3. A coherent receiver is about 20 dB more sensitive than a normal receiver, so the distance that is not relayed in the transmission system becomes longer, which reduces the number of amplifications in the transmitted light path.

Based on the above reasons, coherent optical communication can reduce the cost of optical fiber erection for long-distance transmission, simplify optical path amplification and compensation design, and become the main application technology of current long-distance transmission network.

Application Scenarios of Coherent Optical Modules

At present, the coherent optical communication is mainly used on the line side of the backbone network and the metropolitan area network, and belongs to the technical research field of DWDM long-distance transmission. In the application scenarios of the metropolitan area network and the core network with distance more than 80km, the coherent optical communication features good performance of Optical Signal-to-Noise Ratio (OSNR), sensitivity, dispersion tolerance and so on.

Coherent Applications: DWDM Long-Haul Transmission

WDM System

The operating wavelength range is C-band (1530nm to 1565nm), and the fiber type is G.652D (prefered) or G.655. The key performance index is OSNR.

Error correction coding technology can jump out of the limitations of the physical layer of transmission, and compensate for all physical transmission impairments at the logic layer, especially the effects of nonlinear effects.

Coherent Applications

5G Middlehaul/Backhaul Network

In the 5G middlehaul scenario, 100G/200G DWDM system will be deployed, and the 100G CFP-DCO and 200G CFP2-DCO optical module can be used to implement the 80km scene application; the 400G DCO product is applied in the 5G backhaul scenario with distance less than 200km.


Whether the coherent communication will be used in the DCI field of 40km to 80km depends mainly depends on the commercial cost performance and whether the market capacity is large enough.

At the current 100G rate, products such as 100G ER with EML modulation are sufficient for the use; the 100G CFP-DCO ZR series will appear in the future.

Coherent Applications: Bandwidth by Speed

The OIF organization is developing a 400ZR specification that uses a combination of DWDM and coherent technology.

Andrew Schmitt, principal analyst at Cignal AI, said: “Coherent 400G will limit the development of existing 200G and 100G technologies by 2020, and new devices will maximize optical capacity without relying on coverage.” Foreseeable Yes, more and more 400ZR products will enter the market.


The coherent optical communication system is a more advanced and complex optical transmission system suitable for longer distance and larger capacity information transmission.

At present, coherent modules with the CFP form-factor are bulky and consume large power. Compact coherent modules will replace existing coherent products. The innovation of semiconductor technology and the improvement of chip technology will greatly promote the replacement of 400G coherent products.

In recent years, Gigalight, a global optical interconnect innovator, has increased its research and development of coherent modules and has achieved a series of achievements. In the next few years, it will strengthen cooperation with the industry and jointly promote the progress of related industries.

Source: Analysis of the Current Coherent Optical Module Market

7 Frequently Asked Questions About 200G Active Optical Cables (AOCs)

7 Frequently Asked Questions About 200G Active Optical Cables (AOCs)

1. What Are the Benefits of Using 200G AOCs?

  • To address the need for high-density, high-speed networking solutions
  • To support a variety of next-generation of Ethernet applications
  • The 200G AOCs are crucial to enable hyperscale data centers, service providers and enterprises to meet growing bandwidth demands
  • Backward plug compatible with existing 100G-based systems and flexible port bandwidth for system design

2. What 200G AOCs Are Available on the Market?

Currently, there are only a few suppliers of 200G AOCs on the market, for example, the Gigalight company — a leader in the AOC industry. Gigalight offers a full range of 200G AOCs in both QSFP-DD and QSFP56 form-factors. The Gigalight 200G AOC product line includes 200G QSFP-DD AOC, 200G QSFP-DD to 2x 100G QSFP28 AOC, 200G QSFP-DD to 4x 50G QSFP28 AOC, 200G QSFP56 AOC, 200G QSFP56 to 2x 100G QSFP56 AOC, 200G QSFP56 to 4x 50G SFP56 AOC. All of these cable assemblies are compliant to IEEE standards and industry Multi-Source Agreements (MSAs).

Table 1: The Maximum Data Rates of Gigalight 200G AOCs


The QSFP-DD stands for a “Quad Small Form-factor Pluggable–Double Density”. The QSFP-DD connector also has 8 electrical lanes similar to the QSFP form-factor, but the second row of electrical contacts has been added to the QSFP connector in order to increase the number of high-speed electrical lanes from 4 (in a QSFP) to 8 (in a QSFP-DD).

The QSFP56 stands for “Quad Small Form-factor Pluggable 56 (’56′ refers to the max data rate 56Gb/s each electrical interface can handle)”. The QSFP56 form-factor is a solution for 200G applications. It’s a pluggable form-factor that has the same size as QSFP.

3. Can QSFP56 AOC Support QSFP-DD AOC Ports or Can QSFP-DD AOC Support QSFP56 AOC Ports?

Yes. The QSFP56 is a pluggable form-factor that has the same size as QSFP. The QSFP-DD assemblies are backward compatible with existing QSFP, so your 200G QSFP56 AOC can be used in the 200G QSFP-DD AOC system ports. Your 200G QSFP-DD AOC also can be used in the 200G QSFP56 AOC system ports.

4. What Is the Maximum Distance of 200G AOCs?

For Gigalight’s 200G AOCs, a max length of 100m is supported for both QSFP-DD AOCs and QSFP56 AOCs using OM4 MMF.

Table 2: The Maximum Distances of Gigalight 200G AOCs

5. What Industry Standards Are Associated with 200G AOCs?

The QSFP-DD series AOCs are compliant with the QSFP-DD MSA while the QSFP56 series AOCs are compliant with the QSFP MSA.

6. What Is the Maximum Power Consumption of 200G AOCs?

The maximum power consumption of 200G QSFP-DD AOCs (based on NRZ) is 4w per end while that of 200G QSFP56 AOCs (based on PAM4) is 7w per end.

In general, higher power consumption levels are associated with higher data rates and longer reach.

7. Where Are 200G AOC Used?

The 200G AOCs are suitable for short distances and offer a cost-effective solution to connect within racks and across adjacent racks. While the 200G Direct Attach Cables (DAC) are a low-cost solution for 200GE high-speed interconnects within the reach up to 3 meters only, the 200G AOCs pick it up from there and can reach up to 100 meters. The 200G AOCs are widely used in High-Performance Computing (HPC) and recently became more popular in hyperscale data centers, enterprise and storage systems.

Originally article: 7 Frequently Asked Questions About 200G Active Optical Cables (AOCs)

An Overview of 200G QSFP-DD AOC

An Overview of 200G QSFP-DD AOC

The Market Situation of AOC

Today’s hyperscale data centers and High-Performance Computing (HPC) markets require low-cost solutions for high-performance AOCs for the large-scale adoption of 200G and 400G data rates.

According to a recent report from LightCounting, the multi-mode AOC market will be experiencing significant growth over the next five years in the HPC and large-scale data center applications.

However, the market for 100G AOC is continually growing in the HPC and large-scale data center applications now, and it is still too early to adopt 400G AOC owing to cost and others so that the adoption of 200G AOC is expected to grow in the next years.

AOC and EOM to see revenue growth through 2023 (Source: LightCounting)

In the 200G AOC market, the 200G QSFP-DD AOC is a kind of parallel transceiver optics assembly. It will be the huge potential market and it is possible to replace copper technology in HPC and data center, the reasons include form factor, cost and so on. Next, we will explore them together.

Why Is 200G QSFP-DD AOC More Likely to Be Popular?

The 200G QSFP-DD AOC is a kind of 200G AOC that adopts the QSFP-DD form factor.

QSFP-DD is an eight-channel electrical interface with an additional row of contacts. It is being developed by the QSFP-DD MSA as a key part of the industry’s effort to enable high-speed solutions. The 200G QSFP-DD AOC meets the requirements of QSFP-DD MSA specification.

The QSFP-DD modules are similar to current QSFP. The systems designed with QSFP-DD modules can be backward compatible, allowing them to support existing QSFP modules and provide flexibility for end users and system designers. The 200G QSFP-DD AOC is convenient for end users and system designers.

The Introduction of Gigalight 200G QSFP-DD AOC

Gigalight is one of the rare providers for 200G QSFP-DD AOC. Its 200G QSFP-DD AOC is driving from its innovative optical packaging and the key manufacturing technologies enable scalability, reduced power consumption, increased reliability, and superior module performance for optical communications.

Gigalight 200G QSFP-DD AOC

Features of Gigalight 200G QSFP-DD AOC

  • 8 channels full-duplex 850nm parallel active optical cable
  • Transmission data rate up to 25.78Gbps per channel with integrated CDR
  • Hot-pluggable QSFP-DD form-factor connectors
  • Low power consumption < 4W per end
  • Operating case temperature range 0°C to +70°C

The module block diagram of Gigalight 200G QSFP-DD AOC

Gigalight 200G QSFP-DD AOC adopts self-developed COB (Chip on Board) high-precision technology. The cost of the product is lower and the volume is smaller, which can provide a new generation solution with low cost, low power consumption, high density and high speed for the data center.

Originally article: An Overview of 200G QSFP-DD AOC