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Although 100G PSM4 transceiver and 100G SR4 transceiver appear the same,both use the QSFP28 form factor and MPO-12 interfaces, but their patch cables are completely incompatible. Below Yingda will help clarify their difference for you.
100G PSM4 QSFP28 Patch Cable
100G SR4 QSFP28 Patch Cable
Fiber Type (The Most Fundamental Difference)
- PSM4 (Parallel Single Mode) QSFP28 patch cable requires the use of single mode OS2 patch cords with yellow jacket.
- SR4 (Short Range) QSFP28 patch cable requires the use of multimode OM3/OM4/OM5 patch cords with violet (OM4) or aqua (OM3/OM5) jacket accordingly.
Connector Polishing Method (End-face Geometry)
- PSM4 QSFP28 patch cable connector must use an APC (Angled) polishing endface. The MPO 12 APC connector housing is green. The angled polish is designed to minimize reflection loss for single mode lasers.
- SR4 QSFP28 patch cable connector typically use a PC/UPC (Flat) polishing. The MPO connector housing is typically black, beige, or aqua.
Transmission Distance
- PSM4 patch cables are designed to transmit optical signal within 500 meters or 2km. Therefore, it can be used for medium-to-long-distance interconnection across cabinets, such as DCI.
- SR4 patch cables are designed to transmit optical signal within 70 meters (OM3) or 100 meters (OM4). Therefore, it is typically used for connections within the same server room or cabinet. For example, linking optical transceivers to servers, or interconnecting Top-of-Rack (ToR) switches.
Laser Wavelengths and Principles
• PSM4 transceiver uses 1310nm lasers. Transmits in parallel over 8-fiber single-mode fiber (4 transmit, 4 receive).
• SR4 transcever uses 850nm lasers. Transmits in parallel over 8-fiber multi-mode fiber (4 transmit, 4 receive).
Conclusion
In summary, we can conclude that 100G PSM4 and SR4 QSFP28 patch cables are designed to be used in conjunction with their corresponding optical transceivers. And there are distinct differences between the two optical cables, including fiber types, cable sheath and application scenarios, etc.
| Features | 100G PSM4 QSFP28 Patch Cable | 100G SR4 QSFP28 Patch Cable |
| Fiber Grade | Single-mode OS2 (Yellow) | Multimode OM4/OM3 (Purple/Aqua) |
| Connector Color | Green (APC Polish) | Black/Aqua (UPC Polish) |
| Core Count | 8-Fiber or 12-Fiber (Base-8) | 8-Fiber or 12-Fiber (Base-8) |
| Polarity Standard | Type B (Cross) | Type B (Cross) |
| Interoperability | No (Not Intermateable) | No (Not Intermateable) |
| Primary Applications | Medium-to-Long Distance Interconnects (Up to 500m) | Within 100 meters; Same Data Center/Cabinet |
Note:
- If you connect an SR4 multimode patch cord to a PSM4 transceiver module, or connect a PSM4 green APC patch cord to an SR4 transceiver module, the link will 100% fail to light up (the switch port status will remain “Down”).
- Furthermore, forcibly mating APC (angled) and UPC (flat) connectors will permanently damage the ceramic ferrule inside the optical transceiver module.
