Optical Transceiver Technologies: CWDM4 vs. LR4 vs. PSM4

Among the various optical transceiver technologies, CWDM4, LR4, and PSM4 transceivers are prominent. Each of these technologies has distinct characteristics and use cases. This article explores the differences between CWDM4, LR4, and PSM4, providing a comprehensive understanding of their respective advantages and applications.

CWDM4 (Coarse Wavelength Division Multiplexing 4)

CWDM4 transceivers are designed for data centers and enterprise networks that require moderate to high data rates over moderate distances. They operate using coarse wavelength division multiplexing, which allows multiple wavelengths (or channels) to be combined and transmitted over a single fiber. Here are the key characteristics of CWDM4:

• Data Rate: Typically supports up to 100 Gbps.
• Wavelengths: Uses four different wavelengths, spaced at 20 nm apart.
• Distance: Designed to operate over distances up to 10 kilometers.
• Fiber Type: Utilizes single-mode fiber (SMF).
• Application: Ideal for short to medium-distance data transmission in data centers.

CWDM4 transceivers offer a cost-effective solution for 100 Gbps data transmission, making them suitable for intra-data center connections where distances do not exceed 2 km.

CWDM4 QSFP28 100G transceiver data streams can be de-muxed with passive optical multiplexer, and feed into four CWDM-25G-SFP28 transceivers. Therefore, optical breakout solution is achieved. CWDM4 transceiver scheme:

LR4 (Long Reach 4)

LR4 transceivers are engineered for longer distance data transmission, making them suitable for inter-data center connections or connections within large data centers. They operate on four separate wavelengths over single-mode fiber:

• Data Rate: Supports up to 100 Gbps.
• Wavelengths: Utilizes four different wavelengths (1295 nm, 1300 nm, 1304 nm, and 1309 nm).
• Distance: Capable of transmitting data up to 10 kilometers.
• Fiber Type: Uses single-mode fiber (SMF).
• Application: Best for long-distance data transmission between data centers or within large campuses.

100G QSFP28 LR4 transceivers provide a reliable solution for high-speed data transfer over greater distances, ensuring robust performance and stability for long-range communication. LR4 transceiver scheme:

PSM4 (Parallel Single-Mode 4)

PSM4 transceivers are designed for short to medium-range data transmission within data centers, using parallel single-mode fiber to achieve high data rates. Unlike CWDM4 and LR4, PSM4 transmits data over four parallel fibers, with each fiber carrying a part of the data stream:

• Data Rate: Supports up to 100 Gbps.
• Wavelengths: Operates at a single wavelength (typically 1310 nm) but uses four parallel fibers.
• Distance: Effective up to 2km.
• Fiber Type: Utilizes single-mode fiber (SMF) with MTP/MPO connector.
• Application: Ideal for short-range data transmission within data centers.

PSM4 transceivers offer a straightforward approach to achieving 100 Gbps data rates over shorter distances, leveraging the simplicity and efficiency of parallel data transmission.

100G QSFP28 PSM4 transceiver utilizes a MPO connector, where each link transmits at 25Gbps with 1310nm wavelength. This phenomenon allows to use four 25G-SFP28 1310nm based transceivers at each of the MPO to LC breakout cable end. This allows to introduce breakout solution to the communication system. PSM4 transceiver scheme:

Conclusion

Choosing between CWDM4, LR4, and PSM4 depends largely on the specific requirements of the network, including distance, cost, and infrastructure. CWDM4 provides a balanced solution for moderate distances, LR4 excels in long-distance transmission, and PSM4 is optimized for short-range, high-speed data transfer. Understanding these differences helps network designers and engineers select the appropriate technology to meet their performance and budgetary needs.

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