In the 100G optical module packaging, common types include CFP/CFP2/CFP4 and QSFP28. QSFP28 is the most commonly used packaging due to its smaller size, lower power consumption, and higher density. Common QSFP28 optical modules such as QSFP28 SR4, QSFP28 LR4, QSFP28 PSM4, and QSFP28 CWDM4 can transmit distances ranging from 500m to 10km. For longer distances, the QSFP28 ER4 is needed. The “ER” stands for Extended Reach, capable of transmitting up to 40km.
Working Principle of 100G QSFP28 ER4 Optical Module
The 100G QSFP28 ER4 optical module is designed for 100Gb/s optical communication applications compliant with the Ethernet 100G BASE-ER4 standard. It adopts the QSFP28 multi-source agreement (MSA) form factor and supports digital diagnostics monitoring (DDM). Its design meets the harshest external operating conditions, including temperature, humidity, and EMI interference.
Figure 1: Working Principle of QSFP28 ER4 Optical Module
The module converts 4x25Gb/s electrical data inputs into 4xLAN WDM optical signals, which are then multiplexed into a single channel for 100Gb/s optical transmission. Conversely, on the receiving end, the module demultiplexes the 100Gb/s optical input into 4xLAN WDM optical signal channels and then converts them into 4x electrical output channels.
The center wavelengths of the 4xLAN WDM channels are 1295nm, 1300nm, 1304nm, and 1309nm. High-performance cooled DFB transmitters and high-sensitivity APD receivers provide excellent performance for 100G Ethernet applications, achieving up to 30km links without FEC and up to 40km links with FEC.
Features and Application Scenarios of 100G QSFP28 ER4 Optical Module
High-speed Transmission: With a transmission rate of 100Gbps, it is ideal for handling large amounts of data and connecting various devices and servers, especially in data centers and cloud computing environments.
Long-distance Transmission: “ER” stands for Extended Range, meaning it can stably transmit over long distances, typically up to 40km. This is advantageous in long-distance communication environments, such as in optical communication backbone networks, and also meets modern urban communication speed requirements.
Low Power Consumption: Compared to traditional optical modules, the 100G QSFP28 ER4 optical module generally has lower power consumption, contributing positively to energy conservation and emission reduction.
Compatibility: The 100G QSFP28 ER4 optical module is compatible with various optical fibers and connection methods, making its application more flexible and diverse in different environments.
QSFP28 ER4 Direct Connection Solution
QSFP28 ER4 supports 100G direct connections with a maximum transmission distance of 40km. Simply insert two 100G QSFP28 ER4 modules into the 100G switch ports and connect them using an LC duplex single-mode jumper.
Figure 2: Direct Connection of QSFP28 ER4 Optical Module
Data Center Interconnection Solution
The 100G QSFP28 ER4 optical module is also suitable for connecting data centers located in different geographical locations, supporting high-speed remote interconnection between 100G data centers. It is a convenient and economical interconnection solution. The following diagram shows a basic data center interconnection solution using the 100G QSFP28 ER4 optical module.
Figure 3: Data Center Interconnection with QSFP28 ER4
To achieve 100G long-distance transmission of 40km for enterprises or data centers, whether directly connected or interconnected, the QSFP28 ER4 optical module is applicable.
However, due to the requirement for a BER lower than 1E-12 (without FEC enabled), existing APD technology cannot meet the sensitivity requirements for 100G QSFP28 ER4, and the size of SOA is too large for QSFP28 packaging. Therefore, there are currently no QSFP28 ER4 optical modules on the market that meet these requirements. As a result, many optical module manufacturers in the industry have defined non-standard 100Gbase ER4 Lite modules using QSFP28 packaging, capable of a maximum transmission distance of 40km with FEC enabled and 30km without FEC.
Walsun offers 100G QSFP28 ER4 Lite optical modules that comply with the Ethernet 100Gbase ER4 Lite standard, fully meeting users’ requirements for temperature, humidity, and electromagnetic interference in harsh environments.
