You can determine if an optical module is multimode by checking its labeling, connector color, wavelength, or datasheet specifications.

Visual and Label Indicators

• Labeling: Look for markings on the module. Multimode modules are often labeled as MM or "multimode," while single-mode modules are labeled SM or "single mode" .
• Connector Color: Multimode SFPs typically have orange or aqua-colored connectors, whereas single-mode SFPs usually have yellow or blue connectors .
• Pull Tab Color: Some modules use color-coded pull tabs: black for multimode and blue or yellow for single-mode .

Wavelength and Transmission Distance

• Wavelength: Multimode modules generally operate at 850nm, suitable for short-distance transmission. Single-mode modules operate at 1310nm, 1330nm, 1490nm, or 1550nm, optimized for long-distance transmission .
• Transmission Distance: Multimode modules are typically used for distances under 2 km, often within data centers, while single-mode modules can cover 2 km to over 100 km depending on the SFP type .

Datasheet and Manufacturer Specifications

• Datasheet Check: The most reliable method is to consult the module's datasheet. Look for terms like MMF (Multimode Fiber) or SMF (Single-mode Fiber), which indicate the intended fiber type .
• Product Codes: Some SFPs use codes such as SR for multimode short-range and LR for single-mode long-range .

Practical Tips

• Patch Cable Color: Observing the connected fiber patch cable can provide clues: orange or aqua cables usually indicate multimode, while yellow cables indicate single-mode .
• Avoid Mixing: Do not mix single-mode and multimode transceivers, as they operate at different wavelengths and can cause network issues . By combining these methods—visual inspection, wavelength check, and datasheet verification—you can confidently determine whether an optical module is multimode or single-mode.