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The QSFP 100G PSM4 transceiver (Parallel Single Mode 4-channel) is a single-mode optical module utilizing parallel transmission technology. Unlike LR4 or CWDM4, which operate on 2-fiber cables via wavelength division multiplexing (WDM), it directly runs on 8 fibers, each fiber carrying 25G data.
100G PSM4 Specification
- Transmission distance: up to 500 meters (using G.652 single mode fiber).
- Wavelength: 1310nm.
- Modulation method: 4 x 25G NRZ.
- Physical interface: MPO-12 APC. Note that it must be an APC (angled push-pull) interface, typically with a green connector, to minimize reflection.
- Fiber optic requirement: 8 core single mode fiber (4 transmitters and 4 receivers).
Why choose PSM4 Transceiver?
- Low-cost solution: Since the PSM4 transceiver does not require expensive multiplexers/demultiplexers (MUX/DEMUX) internally, its manufacturing cost is significantly lower than that of CWDM4 or LR4.
- Low consumption: If you are highly concerned about data center cooling and electricity costs (especially when densely populated with modules on high-density switches), the PSM4 is the lowest power consumption option among 100G single mode modules.
- Support QSFP28 to SFP+ breakout: This is its greatest advantage. A PSM4 port can directly connect to four independent 25G SFP28 LR modules via a single MTP to LC breakout cable.
Difference PSM4 vs. CWDM4 vs. DR4
| Item | 100G PSM4 | 100G CWDM4 | 100G DR4 |
| transmission method | Parallel wiring | WDM | Parallel wiring |
| fiber optic interface | MPO-12 (APC) | Duplex LC | MPO-12 (APC) |
| Required optical fiber | 8 core SMF | 2 core SMF | 8 core SMF |
| modulation scheme | NRZ | NRZ | PAM4 |
| Main value | Cheap, support qsfp28 to sfp+ | Save fiber | Docking 400G DR4 through 12 fiber MTP patch cord |
Typical application scenarios
Medium to large data centers: 100G PSM4 transceiver are widely used in large-scale interconnection between Leaf and Spine switches within a range of 500 meters. A PSM4 QSFP28 patch cable is required to convert MPO-12 APC female to MPO-12 APC female.
QSFP 100G PSM4 D Breakout: Split a 100G switch port and directly connect 4 x 25G servers or switches, this is breakout the 100G PSM4 transceiver to four 25G SFP28 LR transceivers by using MPO-12 APC to 4 duplex LC/UPC duplex patch cord.
Notes:
1. Branch compatibility: If you need to split 1 into 4, please confirm whether your switch port supports split or breakout commands.
2. Fiber optic cost: Although the module is cheap, it requires 8-core fiber optic. In the 12 core MPO, PSM4 only uses the middle 8 cores, with 2 cores on each side vacant. If your machine room cables are expensive or fiber optic resources are scarce, using PSM4 will actually increase the overall wiring cost.
3. Fiber type: The original design intention of 100G PSM4 optics is to achieve low-cost parallel transmission on single-mode fiber, so 9/125 μ m OS2 single-mode fiber (usually with a yellow sheath) must be used. It cannot operate on multimode optical fibers (OM3/OM4, navy blue/purple).
4. Interface matching: MPO APC patch cord must be used. PSM4 uses a single-mode laser and is extremely sensitive to echo reflection. APC (Angled Physical Contact) is an 8-degree angled surface polishing that effectively reduces reflection. If a regular MPO UPC (blue head) patch cord is inserted, it will cause high return loss, interfere with the normal operation of the laser, and lead to unstable links.
5. Distance limit: 100G PSM4 transceiver is strictly limited to within 500 meters. Beyond this distance, signal attenuation and delay offset (Skew) can cause link failures.