23Jan, 2024
    Exploring the Advantages of 200G (8x25G NRZ) Optical Technology in Data Centers

    GIGALIGHT, which has focused on optical communication for eight years, directs your attention to the 200G (8x25G NRZ) technology, delving into its advantages such as low power consumption, low latency, and easy deployment. This provides a deeper understanding of cost-effective optical interconnection solutions within data centers.

    There are two technological directions for 200G optical modules: one utilizes the QSFP-DD packaging for an economical 8x25G NRZ network, while the other employs QSFP56 packaging for a 4x50G PAM4 network (to be discussed in a subsequent article).

    Compared to PAM4 technology, 200G (8x25G NRZ) boasts advantages in low power consumption, low latency, and easy deployment.

    Technical details:

    QSFP-DD packaging for 8x25G NRZ network: The 200G optical module uses QSFP-DD packaging, transmitting 25G NRZ signals through 8 channels. NRZ, representing non-return-to-zero signals, involves signal switching between high and low levels. Compared to traditional PAM4 signals, NRZ signals are easier to modulate and demodulate.

    Low power consumption: Utilizing 25G NRZ optical components, the module’s power consumption is reduced by 2–3W compared to modules based on PAM4 DSP CDR technology. This offers significant advantages for data center operational costs (OPEX) and cooling efficiency.

    Low latency: 200G NRZ excels in special application scenarios with stringent network latency requirements, such as high-frequency trading networks. The transmission method of NRZ signals provides an advantage in terms of latency.

    Deployment ease:

    Mature industry chain: The technology of 25G NRZ optical chips and components is relatively mature, providing a reliable foundation for the production of 200G NRZ. This makes the development of related 200G switch ports and optical module products relatively easy, facilitating rapid commercial deployment.

    Low-cost optical interconnection: Due to mature technology and industry chains, 200G NRZ achieves low-cost optical interconnection within data centers. This offers an economically effective solution for the construction and expansion of large-scale data centers.

    200G QSFP-DD SR8

    The 200G QSFP-DD SR8 is a multimode parallel product, utilizing an 8-channel 850nm VCSEL array, compliant with the 100GBASE-SR4 protocol standard. Leveraging the advantages of traditional VCSEL platforms, GIGALIGHT has adopted a simple, efficient, and reliable fiber coupling process. By introducing a 45° prism between the laser and the fiber, along with special material treatment on the fiber surface, the fiber coupling efficiency has been increased to over 80%.

    200G QSFP-DD PSM8

    The 200G QSFP-DD PSM8 is a high-speed product utilizing single-mode parallel technology. In comparison to wavelength division multiplexing (WDM) technology, PSM technology offers cost advantages. GIGALIGHT PSM optical module enables error-free long-distance transmission up to 10km, five times the distance achieved by traditional PSM optical modules.

    200G QSFP-DD LR8

    The 200G QSFP-DD LR8 optical module is based on an 8-channel LAN-WDM wavelength division multiplexing design, achieving a 1E-12 bit error rate over a transmission distance of 20km. In the context of high-reliability 5G middle-backhaul transmission systems, the long-term transmission of PAM4 signals may pose challenges such as insufficient bandwidth. The 200G QSFP-DD LR8, however, offers a high-performance, low-latency, and highly reliable channel solution.

    GIGALIGHT has recently made significant strides in optical design, particularly achieving notable success in the development of 800G optical modules. The design includes the completion of 800G SR8/DR8. For more details, please refer to here. Moreover, GIGALIGHT has successfully mass-produced and deployed 8-channel optical products in niche markets globally, encompassing various fields such as 200G, 400G, and 800G. Visit our official website for further information.

    9Jan, 2024
    200G: Where Bandwidth Meets Technological Evolution

    After the widespread use of 100G data centers, 200G and 400G data center technologies emerged. Overall, people hope that the per-bit cost of investing in 200G and 400G data centers will be on par with 100G. However, in reality, since different data center business models and transmission latency requirements exist, cost is just one mainstream consideration for customers. The primary focus is on meeting business needs with comprehensive cost-effectiveness. The industry is designing various 200G and 400G data center optical interconnect products based on different application demands.

    Two Different 200G Data Center Architectures have been developed.

    1. 200G 8x25G NRZ: Due to the prevalence of 25G NRZ in existing networks and the demand for low latency, the 8x25G NRZ architecture is suitable for achieving 200G data transmission.

    2. 200G 4x50G PAM4: The new network constructions without specific performance requirements, and equipment cost savings can be achieved by using PAM4 chipsets, enabling the application of PAM4 technology. Hence, the 4x50G PAM4 architecture is suitable for achieving 200G data transmission.

    The two different architectures of 200G Ethernet optical modules and their corresponding application scenarios are listed below.

    200G (8x25G NRZ):

    -200G QSFP-DD SR8 (Low latency, common in intra-rack interconnections and interconnections between TOR switches and server network cards).

    -200G QSFP-DD PSM8 (Low latency, interconnections between racks with an abundance of single-mode fibers).

    -200G QSFP-DD 2xCWDM4 (Low latency, interconnections between racks while significantly reducing the use of single-mode fibers).

    200G (4x50G PAM4):

    -200G QSFP56 SR4 (Common in intra-rack interconnections and interconnections between TOR switches and server network cards).

    -200G QSFP56 DR4 (Interconnections between racks with an abundance of single-mode fibers).

    -200G QSFP56 FR4 (Interconnections between racks while significantly reducing the use of single-mode fibers).

    What are the advantages of 200G compared to 100G?

    1. 200G (8x25G NRZ) VS 100G: The physical delay of 8x25G NRZ 200G optical modules is extremely low. It has twice the channels compared to 100G, resulting in approximately double the power consumption and slightly higher costs. However, customers are not only seeking lower prices but also overall cost-effectiveness, making 200G slightly advantageous.

    2. 200G (4x50G PAM4) VS 100G: Compared to 100G optical modules, 4x50G PAM4 provides 2x capacity on a single port while achieving cost-effectiveness (This has actually been achieved)

    What are the advantages of 200G compared to 400G?

    Compared to 400G data centers, 200G data centers require lower investments, have lower technical complexities and costs, and offer relatively higher cost-effectiveness. Although 400G provides higher transmission efficiency, its high deployment and maintenance costs and low localization rate limit its application.

    Thanks to breakthroughs in domestic manufacturers’ optical communication technology, the localization rate of 200G data centers has significantly increased. This reduces dependency on imports, enhances the independent controllability of data center technology in China, lowers the construction and operational costs of 200G data centers, and improves their cost-effectiveness.

    In summary, 200G data centers have their irreplaceable advantages. In terms of cost-effectiveness or the long-term, 200G data centers remain the superior choice. Their low power consumption and significant technological benefits are especially valuable for underdeveloped countries or enterprise-level data centers, making 200G the preferred option.

    200G PAM4 DML VS 200G PAM4 EML:

    To promote the development of economical data center technology, GIGALIGHT recently launched the 200G DR4/FR4 optical modules based on 200G PAM4 DML. How does this upgrade compare to the old version using EML?

    200G PAM4 DML and 200G PAM4 EML are primarily used for a distance of 2km, with 50G PAM4 DML achieving cost and power consumption advantages. The 50G PAM4 DML, providing cost and power consumption advantages compared to 50G PAM4 EML, requires a TEC temperature control circuit to maintain a constant operating temperature for the EA electro-absorption modulator. By contrast, 50G PAM4 DML eliminates the need for this, reducing design complexity, cost, and product power consumption.

    For example, the 200G QSFP56 FR4 DML version has a power consumption of 5W, making it more energy-efficient and cost-effective than the EML version.

    With the development of DML technology, especially in 50G PAM4 2km systems, the performance gap between DML and EML has decreased. With low-consumption, cost-effectiveness and simple manufacture, GIGALIGHT’s 50G PAM4 DML laser excels at applications in large-scale data centers while maintaining compatible metrics. The receiving OMA sensitivity and TDECQ (dB) indicators of the 200G QSFP56 FR4 DML version fully meet the protocol and the current application indicators of 200G FR4 2km transmission.

    As the leader of open optical network devices, GIGALIGHT advocates the vigorous development of economical data center technology. In order to implement this concept, we have launched a full range of 200G QSFP-DD and 200G QSFP56 data center optical transceiver products to further highlight the advantages of 200G in the field of economical data centers.

    26Dec, 2023
    Revolutionizing Data Centers: GIGALIGHT’s Advanced 800G Solutions Reshape Optical Connectivity for AI

    GIGALIGHT released a marketing report highlighting the imminent transformation in data center network architecture driven by the burgeoning adoption of AI applications recently. This shift has spurred investments in data center infrastructure, propelling growth in the 400G/800G optical module market.

    With the release of several 800G switch chips and the gradual deployment of 800G optical modules, the focus now lies in enabling data centers to seamlessly operate at this high 800G rate. This involves selecting the right optical components and cables while considering crucial factors such as bandwidth, distance, and cost.

    Given that AI heavily relies on parallel computing, the article proceeds to explore parallel wiring solutions for 800G data centers, specifically delving into DACs (Direct Attach Cables), AOCs (Active Optical Cables), and optical modules.

    800G Data Center DAC & AOC Solutions

    When it comes to ultra-short-distance applications, DACs and AOCs emerge as preferred choices. These modules directly link to cables, offering easy installation and cost efficiencies compared to optical module solutions. DACs, notably the most cost-effective, have shorter connection distances. Both DACs and AOCs are available in two variations: direct and breakout connections.

    Using DAC as an example, the maximum transmission distance is 2m (PCC)/5m (ACC), replaced by AOC extend up to 100m.

    800G Data Center Multimode Optical Module Solutions
    Multimode optical module connectivity mirrors AOC solutions, both capable of achieving connections up to 100m. The difference lies in the requirement for multimode optical modules to be paired with MPO multimode fibers.

    800G Data Center Single-mode Optical Module Solution
    For long-distance 800G data center setups, GIGALIGHT employs silicon photonics. Compared to conventional 8-lane EML-based 800G optical modules, silicon photonics modules require fewer lasers. For instance, the 800G DR8 utilizes just one laser to achieve lower power consumption without compromising performance. Besides the 500m reach of the 800G DR8 optical module, GIGALIGHT has also introduced the 800G DR8+ for 2km transmission and the 800G DR8++ for 10km transmission, available in OSFP and QSFP-DD packaging options.

    GIGALIGHT offers QSFP-DD packaging options for all the aforementioned solutions.

    The deployment of 800G data centers demands careful consideration of various cable types and their specific characteristics. Different 800G wiring solutions come with distinct advantages, and the choice should align with the specific requirements of the data center.

    Explore more interconnect architectures for AI applications at https://www.gigalight.com/news-events/reports-7329.html

    11Dec, 2023
    Cloud Storage: Transforming Data Management for Agility

    During the digital era, data is increasingly becoming the cornerstone asset for enterprises, experiencing exponential growth in volume. This surge in data has led to high costs for businesses using traditional storage technologies, prompting the emergence of a new approach to storage — cloud storage.

    Cloud storage involves enterprises and individuals leasing third-party storage space at a certain cost for data storage. Through network technology or distributed file systems, cloud storage aggregates various types of storage devices within the network through application software, collaboratively providing data storage and business access functions. Core technologies of cloud storage encompass virtualization, distributed storage, Software-Defined Storage (SDS), and Hyper-Converged Infrastructure (HCI) storage.

    Traditional storage technologies evolved to meet the demands of enterprise data centers, databases, enterprise applications, and virtualization integration. They fulfilled traditional enterprise application requirements for reliability, performance, capacity, and business continuity. However, in the face of cloud computing and the big data era, scalability and concurrent processing performance have become somewhat limited.

    Active suppliers globally offering traditional storage solutions include DELL-EMC, NetApp, HPE, Huawei, HDS, IBM, Fujitsu, and others.

    The emergence of technologies like big data, cloud computing, and virtualization has made traditional IT architectures inadequate to meet enterprise data storage needs. Hence, SDS and HCI infrastructures have emerged and expanded from small and medium-sized enterprises to large corporations.

    According to Fortune Business Insights, the global cloud storage market reached $702 billion in 2021. As the cost advantages of cloud storage solutions become more apparent, it will drive enterprises to further adopt cloud storage. The global cloud storage market is estimated to reach $834 billion in 2022, with an expected growth to $376.4 billion by 2029, at a compound annual growth rate of 24.0%.

    Moving forward, Software-Defined Storage (SDS), distributed storage, and Hyperconverged Infrastructure (HCI) will continue their upward trajectory, becoming pivotal for the future of cloud storage.

    Software-Defined Storage:

    Firstly, the significant trend in SDS development revolves around the application of flash memory. SDS development relies on hardware advancements, wherein the rapid progress of generic hardware lays the foundation for SDS ascension. Utilizing and optimizing flash memory assists SDS products in handling large-scale workloads for enterprise users. To meet the digital demands of enterprise users with lower costs and superior performance, SDS solution providers enhance product performance through continuous technological advancements, leveraging innovative storage technologies like NVMe-oF and 3D XPoint.

    Secondly, SDS will decouple storage system software and hardware. This allows generic hardware to replace proprietary hardware, reducing the threshold for storage system utilization. The rise of open-source frameworks accelerates the expansion of open SDS projects, with open-source initiatives like OpenStack and RedHat leading the way in open-source SDS development. In the control plane, applications like OpenSDS and OpenStack Cinder have matured. In the data plane, high-performance, highly reliable, and scalable open-source software like Ceph, GlusterFS, and Swift find extensive industry applications.

    Faced with new storage demands like massive unstructured data, traditional storage systems exhibit drawbacks of low flexibility, inadequate scalability, and high costs. Users are gradually inclining toward open-source distributed storage.

    Open-source SDS possesses several advantages:

    1. Driven by the open-source community, developers and contributors strive for innovation, technological implementation, and building solution ecosystems, actively promoting the development of open-source SDS technology.

    2. Enterprises can use enterprise-grade technology with higher quality, stability, and security compared to proprietary systems at lower costs.

    3. Open-source SDS decouples storage systems from hardware, allowing users to freely deploy storage platforms and flexibly expand storage devices. Utilizing proprietary storage systems binds users to a single vendor, whereas the use of open-source software enables users to freely choose vendors, realizing the true potential of software-defined storage.

    Distributed Storage:

    Distributed storage systems disperse data storage across multiple independent devices. Distributed network storage systems use a scalable system structure, utilizing multiple storage servers to share storage loads and location servers to locate storage information. It not only enhances system reliability, availability, and access efficiency but also facilitates scalability. Characteristics of distributed storage systems include:

    1. Scalability: Distributed storage systems can scale to clusters of several thousand servers, with the overall system performance growing linearly.

    2. Low cost: The automatic fault tolerance and load balancing features of distributed storage systems enable them to be constructed on low-cost servers. Additionally, linear scalability reduces server costs, enabling automatic operation and maintenance of distributed storage systems.

    3. High performance: Both for individual servers and the entire distributed storage cluster, distributed storage systems require high performance.

    Moreover, similar to how not all SDS is necessarily distributed, distributed storage systems are not always software-defined; they might be hardware-bound. For instance, IBM XIV storage, essentially a distributed storage, is delivered through dedicated hardware, thereby retaining hardware bindings and presenting high-cost issues.

    Hyper-Converged Infrastructure (HCI):

    Hyper-convergence refers to the process of integrating storage, computing, and network connection resources into a single IT framework system, aiming to reduce data center complexity and enhance scalability. This infrastructure amalgamates many advantages of Software-Defined Storage (SDS) and distributed storage. It represents a novel deployment architecture in a virtualized environment by internalizing external storage arrays within servers, sparking an industry shift that profoundly influences the existing IT landscape. Embracing the “hyper-converged architecture” is envisioned as a rational mode for deploying fundamental systems. The hyper-converged architecture is more encompassing than the mere software-defined storage hierarchy, as it covers a wider spectrum and to some extent encapsulates software-defined storage.

    However, hyper-convergence is still in a developmental phase. Despite rapid market expansion, the involvement of numerous vendors and the absence of standardized hyper-converged products pose challenges. Many products currently in the market are relatively new and necessitate continual iterations to enhance stability and sustainability.

    The diverse needs of hyper-converged customers range from requiring substantial storage capacities to necessitating high-computing systems. Yet, existing hyper-converged products often remain too singular and fail to meet the needs of all customers. Moreover, integrating hyper-converged systems with traditional legacy devices poses challenges, with issues concerning the seamless integration of old and new systems remaining a critical concern.

    Conclusion

    The versatility of cloud storage has opened a new chapter in providing organizations with more efficient, scalable, and adaptable data management solutions. The continued evolution of cloud storage is not just a technological shift, it is a transformative force that is propelling organizations into a more agile and competitive future in a data-driven era.

    20Nov, 2023
    Decoding QSFP-DD Module CMIS Protocol and DDM Functionality

    QSFP-DD (Quad Small Form-factor Pluggable Double Density) modules are a common standard in high-speed data communication. They feature a small size and high-density interface, supporting rapid data transmission like Ethernet and fiber channels. Communication and management between QSFP-DD modules and devices are realized through the CMIS protocol. Within the CMIS protocol, DDM plays a crucial role, offering real-time monitoring and reporting of the module’s operational status and performance. This article aims to provide a comprehensive breakdown of the CMIS protocol and DDM functionality in QSFP-DD modules.

    Overview of QSFP-DD Modules

    QSFP-DD modules are multi-channel optical modules capable of transmitting and receiving multiple optical signals simultaneously. They are predominantly utilized in high-density data centers and network equipment such as servers, switches, and routers.

    Overview of CMIS Protocol

    CMIS (Common Management Interface Specification) protocol is a communication protocol designed for managing and monitoring optical modules. It defines the interface and data format between optical modules and system management software. This enables system management software to configure, monitor, and manage optical modules through the CMIS interface. The CMIS protocol encompasses several key aspects:

    CMIS Interface: It establishes the physical connection between the optical module and system management software. QSFP-DD modules use an electronic connection method, connecting the module to the system management software through electronic interfaces.

    CMIS Data Format: CMIS defines a standardized data format and encoding mechanism for data interaction between optical modules and system management software. This format includes configuration information, operational status, performance metrics, and more.

    CMIS Commands and Responses: The protocol defines a series of commands and corresponding responses used for communication between optical modules and system management software. System management software can request specific information from optical modules by sending commands, and the modules respond accordingly.

    Overview of DDM Functionality

    DDM (Digital Diagnostics Monitoring) is a crucial feature within the CMIS protocol, responsible for real-time monitoring and reporting of an optical module’s operational status and performance. DDM monitors various parameters, including input/output optical power, temperature, voltage, among others.

    DDM Sensors and Monitoring Circuitry: Integrated within the optical module, a set of sensors and monitoring circuits track changes in multiple parameters. These components convert monitored data into digital signals, transmitting it via the CMIS interface to system management software.

    Parameter Monitoring and Reporting: Through DDM, system management software acquires real-time parameter data from the optical module, encompassing input/output optical power, temperature, voltage, etc. These metrics aid in fault detection, performance optimization, and network management.

    Applications and Advantages of DDM

    Fault Detection and Maintenance: Real-time monitoring of the optical module’s operational status and performance, such as input/output optical power, allows for swift issue identification and resolution, enhancing system reliability and stability.

    Performance Optimization and Adjustment: Monitoring changes in input/output optical power assists in understanding signal attenuation. Adjusting attenuation coefficients aids in optimizing transmission performance, elevating data transfer reliability and speed.

    Network Monitoring and Management: Integrated with network management systems, DDM enables remote monitoring and management of optical modules. Network administrators can promptly access DDM data, facilitating fault detection, performance optimization, and ultimately improving network reliability and stability.

    Limitations and Challenges of DDM Functionality

    Despite the numerous advantages of DDM functionality, several limitations and challenges exist, as outlined below:

    Data Parsing and Presentation: The data generated by DDM functionality is typically complex, requiring system management software to accurately parse and display this information. Parsing and displaying data may involve different data formats and unit conversions, necessitating corresponding functionality and algorithms within the system management software.

    Data Accuracy and Consistency: Ensuring the accuracy and consistency of DDM functionality is crucial for data reliability and comparability. Variations in optical module characteristics and manufacturing processes across different vendors may lead to inconsistencies and biases in data. This demands that system management software handle such differences to provide accurate and consistent data.

    Compatibility and Interoperability: Implementing CMIS protocols and DDM functionality requires collaboration and compatibility between vendors. Different vendors may have varying CMIS implementations for their optical modules, potentially resulting in compatibility and interoperability issues.

    The CMIS protocol and DDM functionality of QSFP-DD modules offer a standardized interface and method for managing and monitoring optical modules. Through the CMIS interface, system management software can configure, monitor, and manage optical modules. DDM functionality aids in real-time monitoring of an optical module’s operational status and performance, facilitating fault detection and performance optimization. However, it’s essential to be mindful of the limitations and challenges of DDM functionality to ensure its effective and proper utilization.

    30Oct, 2023
    Exploring 400G Optical Module Typical Applications

    With the maturity of industry standards and the continuous growth of network demands, 400G optical module technology has become a vital engine driving the upgrade of the Information and Communications Technology (ICT) industry. It has gained increasing attention and widespread application. It has vast prospects in various application scenarios, including data center networks, metropolitan transport networks, and long-distance high-capacity transmission networks. This article will provide a detailed perspective on 400G optical modules in three typical application scenarios: data center networks, metropolitan transport networks, and long-distance high-capacity transmission networks.

    400G Optical Module Application in Data Center Interconnection Background

    Rapid Growth of East-West Traffic According to IDC data, it is expected that by 2025, nearly 80% of global data traffic will be stored in core and edge servers. Simultaneously, the growth rate of east-west traffic within data centers will be significantly higher than that of north-south traffic and inter-data center traffic. Traditional data centers are gradually being replaced by cloud data centers, driven largely by the popularity of cloud computing, which has stimulated the industry’s demand for 400G optical modules.

    Table 1, Comparison of different types of data centers

    Trends: Reduction in Cost per Bit and Power Consumption

    In general, customer demands adjust in response to changes in application scenarios. For long-distance WDM transmission, module performance is a key factor as customers seek higher capacity and longer transmission distances. In contrast, in short-distance transmission scenarios within data centers, cost is of greater importance to customers.

    To achieve higher capacity, there are three main ways in which 400G optical modules reduce the cost per bit:

    1. PAM4 Technology: PAM4 technology effectively improves bandwidth utilization. Under the same bit rate conditions, PAM4 signals have twice the bit rate of NRZ signals, thus increasing transmission efficiency while reducing costs.
    2. Multi-Channel: An 8-channel transmission solution is more advantageous in terms of balancing cost and power consumption compared to 4-channel transmission.
    3. Higher-Rate Optical Chips: These optical chips can increase transmission speed without affecting the transmission distance. Various 25G-rate optical chips (DML, EML, VSCEL) are gradually upgrading to 56G-rate optical chips.

    400G optical modules find extensive applications in data centers. For instance, the 400G QSFP-DD XDR4 optical module can be used in 4x100G breakout scenarios for QSFP28-FR-100G. For data center interconnection applications, the 400G QSFP-DD FR4 optical module can support 2km single-mode fiber transmission. The 400G QSFP-DD LR8 and 400G QSFP-DD LR4 optical modules, on the other hand, support link lengths of up to 10km by transmitting 4 CWDM wavelengths. Additionally, the 400G QSFP-DD ER8 optical module, suitable for long-distance transmission, can cover 40km of G.652 single-mode fiber links.

    Applications of 400G Optical Modules in Metropolitan Area Carrier Networks

    Background: Traffic Growth Driven by New Technologies in the 5G Era

    Carrier networks are experiencing growing demands in the 5G era, including ultra-high bandwidth, massive connections, ultra-low power consumption latency, and high reliability. Existing urban networks’ 100G ports can no longer meet the transmission requirements for core and aggregation layers. Therefore, 400G optical module solutions play a significant role in 5G carrier networks.

    Table 2, Bandwidth requirement of optical modules in 5G Metro Carrier networks

    Trend: Reducing the Unit Bit Transmission Cost to Improve Reliability and Transmission Distance

    Due to the anticipated high volume of optical modules in 5G base stations, network operators urgently need to lower the optical module costs in network construction investments. Furthermore, in the telecom carrier network, where optical modules have a lifespan of over 10 years and can transmit over 80km, there are higher demands for reliability and performance in metropolitan carrier network applications.

    Metropolitan Carrier Network Applications

    To achieve higher transmission rates and lower production costs, 400G optical modules used for integrated metropolitan carrier networks employ similar technologies to those in data center network scenarios:

    • High-Reliability Optical Modules: Utilizing sealed packaging to meet the 10-year lifespan and operating temperature range of 0~70°C requirements.
    • High-Performance LWDM Transmitters: Low dispersion costs and outstanding transmission performance.
    • High-Performance APD Receivers: Enhancing reception sensitivity.
    • Coherent Technology: To enable transmission distances beyond 80km, 400G optical module solutions employ coherent technology. Simultaneously, with the development of SiP and INP integration technologies and the continuous evolution of CMOS technology, coherent optical modules are becoming smaller and more power-efficient. The advantages of low power consumption and compact size in 400G ZR optical modules are expected to be widely applied in metropolitan network edge access scenarios.

    400G Optical Module Applications in Long-Distance High-Capacity Transmission Networks

    Background: Increasing Bandwidth Pressure for Long-Distance Data Transmission due to Traffic Growth

    The growth in network traffic has increased the bandwidth pressure on transmission networks. For long-distance and high-bandwidth transmission, the use of coherent transmission technology in 400G optical modules with wave division multiplexing (WDM) provides an optimal solution.

    With the introduction of flexible modulation and grid technologies, dense wave division multiplexing (DWDM) enhances spectral efficiency and transmission capacity by selecting the most suitable coding methods and channel widths for each port’s capacity and transmission distance.

    Trend: Improved Spectral Efficiency

    Coherent optical modules are advancing in three aspects:

    1. Spectral Efficiency: Progress in oDSP algorithms enhances spectral efficiency and single-fiber capacity.
    2. Bit Rate: Increasing the single-wavelength bit rate to achieve higher single-port bandwidth, thereby reducing unit bit cost and power consumption.
    3. Smaller Size and Lower Power Consumption: Using integrated optoelectronic components, advanced manufacturing processes, and specialized oDSP algorithms to reduce the size and power consumption of 400G optical modules.

    Conclusion

    Currently, mainstream 400G optical modules are widely used in various network scenarios, including data center networks, metropolitan carrier networks, and long-distance high-capacity transmission networks. The demand for higher capacity, lower unit bit cost, and lower power consumption is driving optical modules towards higher data rates.

    31Aug, 2023
    What a Linear Drive Module is?

    Amidst the high-speed optical module landscape, the incorporation of DSP chips for signal processing has been the norm. These chips, featuring ADC/DAC, FEC, retiming, reshaping, adaptive equalization, and more, hold immense power, yet their potency comes at the cost of significant power consumption and expenses. A typical 7nm DSP in a 400G optical module consumes around 4W, constituting 50% of the module’s power consumption.

    DSP Function Block Diagram

    The following figure shows the power consumption breakdown of a 400G ZR optical module, with a similar scenario for an IMDD.

    As a response to the need for efficiency, the revolutionary concept of Linear-drive technology emerged.

    How can the power consumption and cost impact caused by DSP be mitigated?

    By forgoing DSP within the optical module and integrating its functions into switching chips, a streamlined design emerges. The result? A compact configuration housing only driver and TIA components. Diverging from the traditional driver and TIA functions, those in the Linear Photonic Optics (LPO) architecture include CTLE and Equalization features, facilitating signal compensation. Notably, the Linear Drive concept obviates the need for retiming, eliminating non-linear processes and thus dubbed the Non-retimed module.

    LPO’s merits encompass several facets:

    • Low Power Consumption: LPO yields a 50% reduction in power consumption compared to pluggable optical modules, aligning closely with CPO power levels.

    The overall power consumption of the switch system will be reduced by about 25 percent, as below.

    • Low Latency: Omitting DSP significantly reduces system latency, ideal for latency-sensitive scenarios like inter-GPU communication within High-Performance Computing (HPC) centers.
    • Cost Efficiency: The absence of 5nm/7nm DSP chips translates to cost savings. In an 800G module, the Bill of Materials (BOM) cost totals around $600-$700, with DSP chips accounting for approximately $50-$70. While EQ integration within Driver and TIA adds $3-$5, the total system cost reduction amounts to around 8%.
    • Hot-Pluggability: LPO retains the convenience and reliability of pluggable modules, leveraging established optical module supply chains. This distinguishes LPO from CPO, which is still less widely adopted due to reliability and cost considerations.
    Comparison of various dimensions of conventional optical modules, LPOs and CPOs

    In summary, LPO represents a novel approach with its unique advantages and ongoing challenges.

    1. Integration of DSP Chips: To implement LPO, there’s a need to integrate DSP chips into switches, which requires the involvement of switch chip manufacturers. The LPO concept has also stirred the competition among DSP chip manufacturers, such as Broadcom and Inphi.
    2. New Protocols and Testing Methods: Introducing LPO necessitates the development of new protocols and testing methods. The Optical Internetworking Forum (OIF) is currently working on defining the CEI-112G-LINEAR standard to address this need.
    3. Applicability and Distance: One concern is whether LPO is suitable for longer distances, potentially reaching kilometers. As DSP chips are no longer present in the module, there may be a decrease in error performance, leading to a reduction in transmission distance.

    While several companies showcased their linear-drive solutions, particularly during OFC 2023, and launched LPO options post-event, the transition from technical discussions to widespread adoption is ongoing. The introduction of LPO underscores the industry’s pursuit of low-power, low-cost, high-speed optical modules.