Common Interface Standards and Rates of Optical Port Switches

The core of an optical port переключатель’s interface lies in its optical modules, while the ports on the switch panel (such as SFP/SFP+/QSFP28 slots) are designed to accommodate these modules. Therefore, the interface standard is jointly determined by the type of optical module used and the transmission medium (fiber optic type).

Below are common interface standards and types, arranged in ascending order of data rate:

1. Gigabit Ethernet (1G / 1000M)

This is the most common basic optical port type.

• Interface/Slot Type: SFP (Small Form-factor Pluggable), commonly known as “small port” or “gigabit optical port”.
• Common Optical Module Standards:
  • 1000BASE-SX: Uses Multimode Fiber (MMF), with a typical transmission distance of 550 meters (when using OM2 fiber).
  • 1000BASE-LX: Compatible with both Multimode Fiber (550-meter transmission) and Singlemode Fiber (SMF, up to 10 km transmission).
  • 1000BASE-ZX: Uses Singlemode Fiber, with a transmission distance of 70-80 km.
• Fiber Optic Type Used: Multimode Fiber (OM1/OM2/OM3/OM4) or Singlemode Fiber (OS2).
• Interface Connector: Usually LC duplex; a few older devices use SC duplex.

2. 10-Gigabit Ethernet (10G)

Currently, it is the mainstream rate for the core of data centers and enterprise networks.

• Interface/Slot Type: SFP+ (Enhanced Small Form-factor Pluggable). SFP+ slots are backward compatible with SFP optical modules (but the data rate will drop to 1G).
• Common Optical Module Standards:
  • 10GBASE-SR: Uses Multimode Fiber (OM3/OM4), with transmission distances of 300 meters (OM3) and 400 meters (OM4) respectively.
  • 10GBASE-LR: Uses Singlemode Fiber, with a transmission distance of up to 10 km.
  • 10GBASE-ER: Uses Singlemode Fiber, with a transmission distance of up to 40 km.
  • 10GBASE-ZR: Uses Singlemode Fiber, with a transmission distance of up to 80 km.
  • 10GBASE-T: This is an electrical port standard (using network cables), but some switches also offer 10G-T modules in SFP+ form for short-distance copper cable connections.
• Fiber Optic Type Used: Multimode Fiber (OM3/OM4/OM5) or Singlemode Fiber.
• Interface Connector: LC duplex.

3. 25-Gigabit Ethernet (25G) and 40-Gigabit Ethernet (40G)

These are mainly used for high-speed server access and switch interconnection.

• Interface/Slot Type:
  • 25G: SFP28. It has the same form factor as SFP/SFP+ but supports a 25 Gbps data rate.
  • 40G: QSFP+ (Quad Small Form-factor Pluggable). A single QSFP+ interface integrates 4x10G channels internally.
• Common Optical Module Standards:
  • 25GBASE-SR: Uses Multimode Fiber, with a transmission distance of approximately 70 meters (OM3) / 100 meters (OM4).
  • 25GBASE-LR: Uses Singlemode Fiber, with a transmission distance of up to 10 km.
  • 40GBASE-SR4: Uses Multimode Fiber with an MPO/MTP interface, achieving transmission through 4-core parallel transmission, with a maximum distance of 150 meters (OM4).
  • 40GBASE-LR4: Uses Singlemode Fiber with an LC interface, transmitting 4 wavelengths over a single fiber via Wavelength Division Multiplexing (WDM) technology, with a transmission distance of up to 10 km.
• Fiber Optic Type Used: Multimode Fiber (OM3/OM4/OM5) or Singlemode Fiber.
• Interface Connector: LC duplex (for LR standards) or MPO/MTP (12-core or 24-core, for SR4 parallel transmission).

4. 100-Gigabit Ethernet (100G) and Higher Rates

These are used for data center cores, backbone networks, and high-speed interconnections.

• Interface/Slot Type:
  • 100G: QSFP28. It has the same form factor as QSFP+ but supports 25G per channel, with a total of 4 channels (100G).
  • 200G: QSFP56.
  • 400G: QSFP-DD (Double Density) or OSFP (Octal Small Form-factor Pluggable). QSFP-DD is currently the mainstream.
• Common Optical Module Standards (Taking 100G as an Example):
  • 100GBASE-SR4: Uses Multimode Fiber with an MPO/MTP interface, achieving transmission through 4x25G parallel transmission, with a transmission distance of approximately 70 meters (OM4) / 100 meters (OM5).
  • 100GBASE-LR4: Uses Singlemode Fiber with an LC interface, transmitting 4 wavelengths (25G per wavelength) over a single fiber via WDM technology, with a transmission distance of up to 10 km.
  • 100GBASE-ER4: Similar to LR4, but with a transmission distance of up to 40 km.
  • 100GBASE-DR: Uses Singlemode Fiber and an LC interface, with 100G single-channel PAM4 modulation, achieving a transmission distance of up to 500 meters. It is an emerging low-cost short-distance solution.
• Fiber Optic Type Used: Multimode Fiber (OM4/OM5) or Singlemode Fiber. Singlemode Fiber is widely used for rates of 400G and above.
• Interface Connector: MPO/MTP (for SR parallel transmission) or LC duplex (for LR/WDM transmission). New connectors such as CS and SN have emerged in the 400G era.

Summary Table

Considerations for Selection

1. Совместимость: Ensure the optical module is compatible with the switch brand. Although most switches support third-party compatible optical modules, some brands (e.g., Cisco) may lock to original modules via encryption.
2. Fiber Optic Type Matching: Singlemode Fiber (SMF/OS2) is used for long-distance transmission; Multimode Fiber (MMF/OM3/OM4/OM5) is suitable for short-distance, low-cost scenarios. The two cannot be mixed, otherwise communication failure or device damage may occur.
3. Расстояние передачи: The selected optical module standard must meet actual transmission distance requirements, with a certain margin reserved.
4. Длина волны: Different standards use different wavelengths (e.g., 850nm, 1310nm, 1550nm), which need to match the fiber optic type and transmission distance.
5. Bidirectional Transmission Technology: For example, Bidirectional (BiDi) optical modules use a single fiber to achieve receiving/transmitting via different wavelengths, saving fiber resources.

It is hoped that this detailed overview will help you fully understand the interface standards and rates of optical port switches.