100G LR4, CWDM4, and PSM4 are three common types of 100Gbps optical transceivers, and they are all important components of data center and telecom networks. What are the differences?
This article will explore the main differences between these Optical Modules and help you choose the right one.
Overview of 100G LR4, CWDM4 and PSM4
LR4: Long Range 4 (LR4), is a 100G transceiver with 4 Independent LAN-WDM channels to transmit data over a longer distance. LR4 can achieve a 100Gbps data rate, with a maximum link length of 10km via Single Mode Fiber (SMF).
CWDM4: Coarse Wavelength Division Multiplexing 4 (CWDM4). It is compliant with 100G CWDM4 MSA Specification and an Uncooled 4x25Gb/s CWDM transmitter. CWDM4 can achieve a 100Gbps data rate, with a maximum link length of 2km via Single Mode Fiber (SMF).
PSM4: Parallel Single Mode 4 (PSM4), using a wavelength of 1310nm via a MTP/MPO-12 connector. It is intended for up to 2km or 10km reach service with a four-lane 25.78125G data rate.
What are their differences?
LR4 vs CWDM4
Transmission distance
The 100G LR4 has a maximum transmission distance of 10 kilometers, which can meet the transmission needs of longer distances. The maximum transmission distance of 100G CWDM4 is 2 km, which is more suitable for medium and short-distance transmission.
Wavelength division multiplexing
LR4 uses dense wavelength division multiplexing (DWDM) to achieve a data rate of 100Gbps by using four wavelengths (1264.5nm – 1337.5nm) of signal transmission in optical fibers.
CWDM4, on the other hand, uses coarse wavelength division multiplexing (CWDM) to transmit 100Gbps using signals at four wavelengths (1270nm, 1290nm, 1310nm, and 1330nm). CWDM has a larger wavelength interval than DWDM, resulting in a lower system design and cost.
Application scenarios
100G LR4 is typically used in data center interconnections, metro networks, or other applications that require long transmission distances. CWDM4 is more suitable for scenarios with short distances and higher cost requirements, such as interconnection within or adjacent data centers.
CWDM4 vs PSM4
Transmission mode
100G PSM4 uses parallel transmission through 4 pairs of single-mode fibers (8 fibers, 4 transmitters, and 4 receivers). whereas
CWDM4 uses coarse wavelength division multiplexing, which uses 4 optical signals of different wavelengths to merge in a single optical fiber for single-pair single-mode fiber transmission.
Wavelength
PSM4 uses only one wavelength (typically 1310nm). Whereas, CWDM4 uses 4 different wavelengths (1270nm, 1290nm, 1310nm, and 1330nm).
Fiber type
PSM4 requires the use of 8 fibers in single-mode fiber. CWDM4 requires only 2 fibers (1 pair of bidirectional transmission)
PSM4 vs LR4
Transmission mode
PSM4 uses parallel transmission. The LR4 uses dense wavelength division multiplexing (DWDM).
Fiber type
PSM4 requires 8 fibers of single-mode fiber. The LR4 only requires 2 single-mode fibers (1 pair of bidirectional transmission).
Wavelength
PSM4 uses only one wavelength (typically 1310nm) while LR4 uses 4 wavelengths (1264.5nm – 1337.5nm) to transmit simultaneously on a single fiber via DWDM technology.
100G Optical module | LR4 | CWDM4 | PSM4 |
Distance | 10km | 2km | 2km or 10km |
Wavelength | 4 different wavelengths | 4 different wavelengths | Single wavelength, 4 pairs of parallel fibers |
Optical Transmitter | 4 x LAN WDM EML | 4x DFB | 4x CWDM DML |
Connector | Duplex LC | Duplex LC | MPO/MTP(8-core) |
Application | Long-distance data center interconnection | Mid-distance data center interconnects | Interconnection within short-distance data centers |
How to choose them?
100G LR4 is more suitable for longer transmission distances and higher performance, such as long-distance transmission (up to 10 km) between data centers or in metro networks
CWDM4 is suitable for short-distance transmission distances and where you want to reduce costs, such as short- to medium-distance interconnection within or between adjacent data centers, and is suitable for longer distances (within 2 km).
100G PSM4 is suitable for short-distance and high-bandwidth scenarios in data centers, meeting high bandwidth requirements and reducing module costs.
Conclusion
The choice between 100G LR4, CWDM4, or PSM4 depends on the specific needs of your network. According to the transmission distance, transmission mode, optical fiber type application scenario, and other factors, the selection of modules is determined.
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