200G - GIGALIGHT

21Jun, 2023

GIGALIGHT Redefines 200G Data Centers With Introducing New PAM4 DML-based 200G QSFP56 DR4/FR4 Optical Module

Shenzhen, China, June 21, 2023 – In terms of cost-effectiveness and long-term viability, 200G data centers continue to reign supreme. The advantages of low power consumption and effective technical solutions make them particularly appealing for underdeveloped countries or enterprise-level data centers. As the open optical network devices explorer, GIGALIGHT is dedicated to the development of cost-friendly data center technologies. In line with this vision, GIGALIGHT recently unveiled a 200G QSFP56 DR4/FR4 data center optical module based on the PAM4 DML platform, further solidifying and highlighting the advantages of 200G in certain data center domains.

The new 200G QSFP56 DR4/FR4 module utilizes PAM4 modulation technology and DML lasers to deliver high-speed transmission and exceptional performance. Two versions are available, allowing for selection based on the mid-short distance transmission within the data center. Both the DR4 and FR4 modules have a power consumption of less than 6W, resulting in reduced energy consumption and operational costs. The FR4 module exhibits superior receive sensitivity OMA compared to the DR4 module (by 1dBm), with excellent performance parameters including high OMA sensitivity (<-9dBm). This makes it adaptable to various application scenarios, providing high-quality signal transmission and maintaining a good eye diagram quality under PAM4 modulation.

With the continuous growth of network data and the diversification of application demands, data centers indeed require higher bandwidth and greater scalability. Under the premise of meeting broadband requirements and application needs, the 200G data center demonstrates clear advantages compared to both the 100G and 400G data centers. It is crucial to have an objective understanding of the true meaning of “advantages” and not simply chase after the evaluation based solely on “technological advancements.”

For a comprehensive return on investment in a 400G data center, the only viable path is to adopt a silicon photonics technology platform. As for the emerging star, the 800G data center, it also requires a clear definition of its application scope. It is crucial to understand that 800G represents a diversified data center.

GIGALIGHT has always been committed to providing customers with high-performance, highly reliable, and more cost-effective optical communication solutions. With a rich product line of 200G solutions, including QSFP-DD and QSFP56, the introduction of the upgraded 200G QSFP56 DR4/FR4 optical module offers more cost-effective choices for building high-speed, green data centers.

About GIGALIGHT

As an open optical network device explorer, GIGALIGHT integrates the design, manufacturing, and sales of active and passive optical devices and subsystems. Its products mainly include optical modules, silicon photonics modules, liquid-cooled modules, passive optical components, active optical cables, direct attach copper cables, coherent optical communication modules, and OPEN DCI BOX subsystems. GIGALIGHT focuses on serving applications such as data centers, 5G transport networks, metropolitan wavelength division multiplexing (WDM) transmission, and ultra-high-definition broadcasting and video. It is an innovative high-speed optical interconnect hardware solutions provider.

16Aug, 2022

GIGALIGHT Launches 200G (8 x 25G) QSFP-DD Industrial-grade Optical Modules and Will Follow the Niche Path Through to the End!

Shenzhen, China, August 16, 2022 – GIGALIGHT announces the upgrade of the 200G QSFP-DD SR8/PSM8 optical module to the industrial temperature range. This upgrade can better meet the needs of AI supercomputing and outdoor high-speed signal distribution and transmission scenarios.

GIGALIGHT has gained a wide range of customers in different market segments worldwide after introducing the commercial grade 200G (8X25G NRZ) optical modules in the QSFP-DD form factor 3 years ago. Unlike the 200G QSFP56 XR4/200G QSFP-DD XR4 based on PAM4 modulation, the main features of the 200G QSFP-DD XR8 series include ultra-high density optical design, zero-bit error multi-channel transmission mechanism based on NRZ signal modulation and transmission reliability.

The upgraded 200G QSFP-DD SR8 and 200G QSFP-DD PSM8 adopt industrial-grade optoelectronic chips, which allow three-temperature zero-bit error transmission in the range of -40 to +85 degrees Celsius.

SR8 Three-temperature Margin Distribution

PSM8 Three-temperature Margin Distribution

GIGALIGHT is almost the only supporter of the 8X25G NRZ QSFP-DD optical module series globally, resulting from its insistence on differentiation. The 8X25G NRZ QSFP-DD optical module will surely exist in the history of optical communication as a niche player.

About GIGALIGHT

As the open optical network device explorer, GIGALIGHT integrates the design, manufacture and sales of active & passive optical devices and subsystems. The main products are optical transceivers, silicon photonics transceivers, liquid cooling transceivers, optical passive components, AOC & DAC, coherent optical modules and open DCI BOX subsystems. GIGALIGHT is a hardware solution provider of innovatively designed high-speed optical interconnection that focuses on data center, 5G carrier network, metro WDM transmission, UHD broadcast video and other application fields.

30Jul, 2019

The Evolution Path of Next Generation Data Center’s Optical Interconnection

As a global innovator of optical interconnect design, Gigalight is committed to providing customers with design- and cost-leading high-speed optical interconnect product solutions. Deeply immersed in the field of optical interconnects for more than a decade, Gigalight believes that the upgrade path for next-generation data center optical interconnects should be from 100G to 200G, and then to 400G. Only such smooth upgrades and technological transitions are met the law of market development.

From 100G to 400G, the data center’s network architecture should be firstly upgraded to the most cost-effective 200G SR8/PSM8 architecture (8x 25G NRZ), then to the first generation 400G network architecture—400G PSM8/FR8 (8x 50G PAM4); and at last to the second generation 400G network architecture—400G DR4/FR4 (4x 100G PAM4). Among them, the 200G (8x 25G NRZ) network adopts the mature 25G NRZ electric chip and optical device, which has the same port density as the 100G network, but the bandwidth is doubled, which effectively reduces the transmission cost. In addition, the industrial chain of 25G NRZ optoelectronic chips and optical devices is relatively mature, and the related switches and optical module products are also easier to develop (compared to 50G PAM4), which can help the data center to quickly realize the commercial deployment of 200G networks.

At present, some companies believe that the data center network architecture should be directly upgraded to the second generation 400G, namely the 400G DR4/FR4, so they are rushing to introduce Single Lambda 100G (100G PAM4) or 400G (4x 100G PAM4) optical modules. However, these optical modules require expensive optical components, including Silicon Photonics modulators, EML lasers, and DSP error correction chips. Gigalight believes that it is too early to deploy the 400G DR4/FR4 network architecture in the data center, because the 400G DR4/FR4 products based on Single Lambda 100G PAM4 DSP technology is likely to be out of the Shannon limit, but the 400G PSM8/FR8 products based on 50G PAM4 technology are more likely to meet R&D expectations. The first generation of 400G network (8x 50G PAM4) is easier to commercialize because it adopts 8 channels of 25G linearity optoelectronic chips and related optical devices consistent with the 200G network, except that PAM4 modulation technology is used to achieve doubled bandwidth, and it is just after the 200G NRZ network in the data center network upgrade path.

The network upgrade of the data center should follow the market rules, and there is no such thing as a shortcut to the sky. Gigalight follows the rules of the market, and the 200G (8x 25G NRZ) products that are preferred for data center customers have been validated by North American data center customers. With full R&D design and verification, Gigalight now offers a complete and reliable 200G optical interconnect solution (including the 200G 4x 50G PAM4 series) with the following key benefits in smooth transition to 400G:

Low Power Consumption. With existing 25G NRZ optics, power consumption is as low as 4 watts, while optical modules based on DSP CDR technology can be 2 to 3 watts higher. In this case, saving 2 to 3 watts per 200G optical module is very beneficial for optimizing OPEX and cooling efficiency.
Low Latency. Excellent performance in some special application scenarios such as High Performance Computing (HPC) and High Frequency Trading (HFT).

The 8x 25G NRZ reduces the complexity and design difficulty of the 200G optical module and avoids the development cost and material cost of the difficult DSP. At a broader market level, 100G optical modules have matured and component integration has been established. Similarly, 200G optical modules will also form a cost structure similar to 100G optical modules in the first few years before entering the market, following the downward cost curve. Due to further standardization and automation of component integration and mass production, 200G optical modules are expected to achieve a cost structure comparable to today’s 100G optical modules. Gigalight’s breakthrough in optical packaging technology enables density increases, enabling 200G networks to be quickly and economically deployed commercially!

28Jan, 2019

50G PAM4-based Optical Transceiver Technologies

With the PAM4 encoding technology, the amount of information transmitted on 50G PAM4-based optical transceivers within each sampling cycle doubles. A 25G optical component can be used to achieve a 50Gbps transmission rate, reducing the costs of optical transceivers.

50G PAM4 applies to multiple scenarios, such as single-lane 50GE PAM4 optical transceivers, 4-lane 200GE optical transceivers, and 8-lane 400GE optical transceivers.

Functions

This section introduces the functions of a single-lane 50GE PAM4 optical transceiver.

Working principle of a 50GE PAM4 optical transceiver

The working principle of a 50GE PAM4 optical transceiver is described as follows:

In the transmit direction, the PAM4 encoding chip aggregates two 25Gbit/s NRZ signals into one 25GBaud PAM4 signal. The laser drive chip amplifies the PAM4 signal, and the 25Gbps laser converts the electrical signal into a 25GBaud(50Gbps) single-wavelength optical signal.

In the receive direction, the detector converts the 25GBaud single-wavelength optical signal into an electric signal. The electric signal is shaped and amplified, and then output to the PAM4 decoding chip. The PAM4 decoding chip converts the signal into two 25Gbps NRZ signals.

The 50GE PAM4 optical transceiver uses the QSFP28 encapsulation mode, LC optical interfaces, and single-mode optical fibers. The transmission distance is 10km or 40km, and the maximum power consumption is 4.5W.

Specifications

The performance of transmitters and receivers on optical interfaces of 50GE PAM4 optical transceivers must comply with the IEEE 802.3bs and IEEE 802.3cd standards.

An optical transceiver provides N 25Gbps electrical interfaces. For a 50GE optical transceiver, the two electrical lanes transmit TX1/RX1 and TX2/RX2 signals specified in the SFF-8436_MSA standards. The performance of electrical interfaces must comply with the CEI-28G-VSR LAUI-2 standard.

The optical transceiver with a transmission rate of 50Gbps on a single wavelength supports 50GE, 200GE, and 400GE interfaces. The following table lists the parameters for the 50GE, 200GE, and 400GE technical solutions.

Technical Solutions

Optical Component and Drive Chip

50G PAM4 optical transceivers use mature 25Gbps optoelectronic chips to deliver cost-effective solutions. In 50GBASE-LR 10 km scenarios, uncooled Direct Modulated Laser (DML) Transmitter Optical Sub-Assemblies (TOSAs) with TO packaging are used. Such a solution features mature technologies, low costs, low power consumption, and easy mass production. The linear DML driver chip can convert input PAM4 voltage electric signals into current signals that can directly drive lasers. Such chips deliver a high bandwidth and output large drive current. Their maximum working rate can reach 28GBaud. At the receive end, Receiver Optical Sub-Assemblies (ROSAs) with TO packaging are used. 25Gbps pins and linear Trans-Impedance Amplifier (TIA) chips are integrated to the ROSAs.

Optical components in 50GBASE-LR scenarios

In 50GBASE-ER 40 km scenarios, 25Gbps Electro-absorption Modulated Laser (EML) TOSAs with BOX packaging are used. External cavity modulated Distribution Feed-Back (DFB) lasers, isolators, monitoring diodes, thermistors, and EML components are integrated to the TOSAs and driven by voltage signals. Such a solution features wide linear domains, high ER, high output optical power, and low TDECQ. Linear EML drive chips can amplify input PAM4 signals and output them to next EMLs. These chips provide a high bandwidth, a small jitter, an adjustable output gain, and a working rate up to 28GBaud. At the receive end, APD ROSAs with TO packaging are used. 25Gbps APDs and linear TIA chips are integrated into the ROSAs. Such ROSAs feature high sensitivity and apply to 40km long-distance transmission.

Optical components in 50GBASE-ER scenarios

PAM4 Chip

PAM4 codec chips perform conversion between NRZ signals and PAM4 signals inside transceivers. In the transmit direction, PAM4 chips shape, amplify, and convert two 25Gbps NRZ signals output by boards into one 25GBaud PAM4 signal. In the receive direction, PAM4 chips use the Analog to Digital Converter (ADC) and Digital Signal Processing (DSP) technology to decode the one 25GBaud signal to two 25Gbps NRZ signals.

Differences Between Solutions of NRZ and PAM4 Transceivers

The optical components and chips of PAM4 transceivers are very different from those of NRZ transceivers. The following table lists the differences between 50G QSFP28 LR and 25G SFP28 LR.

The main difference lies in laser drive chips, TIA chips, and data processing chips.

Since PAM4 code has four types of level logic, the laser drive chips and TIA chips are capable of linear outputs. NRZ transceivers output signals in amplitude limiting mode.

PAM4 transceivers use DSP to implement conversion between a 50G PAM4 signal and two 25Gbps NRZ signals. NRZ transceivers transmit data using Clock & Data Recovery (CDR) chips only.