How to Tell if My SFP is Single-Mode or Multimode?

Posted on Mar 21, 2024 by

10G SFP+

To determine if your SFP (Small Form-factor Pluggable) module is single mode or multimode, you can look for specific markings or labels on the module itself. Typically, single mode SFP modules are labeled as "SM" or "single mode," while multimode modules may be labeled as "MM" or "multimode." Additionally, single mode modules often have yellow-colored connectors, while multimode modules may have orange or aqua-colored connectors. It is important to check the specifications or documentation provided by the manufacturer to confirm the mode of your SFP module, as the labeling and color coding conventions may vary.

What is Single-Mode vs. Multimode SFP?

SFP, or Small Form-factor Pluggable, is a type of transceiver used in data communication and telecommunications networks. It allows for the connection of a network device to various types of fiber optic or copper cabling. SFP modules are standardized by the MSA (Multi-Source Agreement), meaning they can be used across different brands of networking equipment. There are two primary types of fiber optic SFP transceivers based on the mode of the fiber: Single-Mode SFP (SMF) and Multimode SFP (MMF).

Single-Mode SFP

Fiber Type: Single-mode fiber (SMF) uses one mode of light to propagate through the fiber. This means there is a single light path and it's usually a laser-based light source.

Core Diameter: A single-mode fiber has a small core diameter, typically around 9 micrometers.

Distance: Single-mode SFP can transmit data over long distances, generally up to 150 kilometers, depending on the SFP model and its optical budget.

Speed and Bandwidth: Single-mode fiber offers higher bandwidth than multimode and can support higher data rates because it has no modal dispersion due to the single light path.

Color Coding: Single-mode SFPs are typically identified by blue-colored bail or coding.

Multimode SFP

Fiber Type: Multimode fiber (MMF) allows multiple modes or light paths to propagate through the fiber, resulting in differential mode delay. This is usually an LED-based light source but can be laser-optimized for higher performance on later multimode fiber versions.

Core Diameter: Multimode fiber has a larger core size, usually 50 or 62.5 micrometers, which enables multiple light paths.

Distance: Multimode SFPs are suitable for shorter distances, generally up to 2 kilometers, but most are used for distances under 600 meters.

Speed and Bandwidth: Multimode SFPs offer high bandwidth at short distances, but the bandwidth potential decreases with increased cable length due to modal dispersion.

Color Coding: Multimode SFPs often have a black or beige bail, or aqua in the case of the enhanced 10Gbps versions (OM3/OM4).

When choosing an SFP for a network application, it's essential to consider the required distance, data rate, compatibility with the existing network infrastructure, and the cost. Single-mode fiber solutions are generally more suitable for long-haul applications, whereas multimode fiber is often preferred for short-range data communications, such as within a data center or a building.

Check the Labeling or Product Specifications of the SFP Module.

To ascertain the mode of your Small Form-factor Pluggable (SFP) module, begin by examining its label or documented specifications. Manufacturers typically specify on these labels or within the documentation whether the SFP module is designed for single mode ("SM") or multimode ("MM") fibers. Look for these indicators in the text to identify the mode.

When the label or specifications do not provide clear insights, consider inspecting the SFP module visually. The physical attributes between single mode and multimode SFP modules differ notably. Single mode modules often allow for greater transmission distances with a fiber core diameter around 9 microns, while multimode modules accommodate less distance and have a broader core diameter, generally 50 or 62.5 microns.

Bear in mind the existence of advanced SFP modules that are equipped to handle both single mode and multimode fibers; these are termed "dual-mode" or "universal" SFPs. This type will automatically adapt to the connected fiber type. When using a dual-mode SFP module, the mode may not be visibly evident, thus necessitating a check of the product's specifics or a consultation with the manufacturer.


To sum up, verifying whether your SFP module is single mode or multimode involves initial scrutiny of labels or specifications, followed by physical examination, and when in doubt, reaching out to the manufacturer for definitive answers.

Outer Appearance Identification - Single-Mode vs. Multimode SFP Color Coding

Single-mode SFP vs multimode SFP is color-coded with different Bale Clasp. Though the color-coding rule is not total conformity for different vendors, generally the Bale Clasp of multimode SFP is black, and fiber patch cables used with multimode SFP are usually orange (OM1/OM2), aqua green (OM3/OM4), green (OM5).


OM2 Multi Mode Fiber Optic Patch Cable

Fig 1: Black color-coded Bale Clasp 1G SFP are multimode SFP, and used with OM1/OM2 multimode fiber patch cables in orange, OM3, OM4 in aqua green, or OM5 in green.

The most common color of single-mode SFP Bale Clasp is blue, there are also some in yellow, red, etc. Fiber optic jumpers used with single-mode optical modules are generally yellow.


OS2 Single Mode Fiber Optic Patch Cable

Fig 2: Blue/Yellow/Red color-coded Bale Clasp 1G SFP are single-mode SFP, and are often used with single-mode fiber patch cables in yellow.

Measuring the Module's Optical Properties with a Power Meter or OTDR

Employ a power meter or an Optical Time-Domain Reflectometer (OTDR) to ascertain the optical attributes of your SFP (Small Form-Factor Pluggable) module and discern whether it operates on single-mode or multimode fiber.

A power meter gauges the optical signal's intensity and can be instrumental in assessing the SFP module's output. Typically, single-mode SFP modules exhibit higher output power than their multimode counterparts. By juxtaposing the empirical power values against the SFP module's specifications, you can infer its mode designation.

Conversely, an OTDR grants a comprehensive analysis of the module's optical performance through parameters like signal loss and reflectance over the fiber's trajectory. Single-mode fibers are generally characterized by reduced signal loss and augmented reflectance in contrast to multimode fibers. An examination of the OTDR's readings facilitates the determination of the fiber mode utilized by the SFP module.

Furthermore, it is prudent to inspect the SFP module for any mode-indicative inscriptions or to peruse its product manual. When necessary, reaching out to the manufacturer may yield definitive confirmation of the module's mode configuration.

With the continuous evolution of technology, alternative mechanisms or updated equipment could emerge for identifying an SFP module's mode. Therefore, engaging with the latest industrial developments and seeking advice from domain experts or authoritative resources is essential for obtaining valid and current assessments.

Seeking Expert Consultation for SFP Module Identification

When attempting to establish if your SFP (Small Form-factor Pluggable) module is single mode or multimode, there are several preliminary techniques you might consider. Yet, for guaranteed accuracy, soliciting help from an expert in the field is highly advised.

  • Label or Manual Review: Typically, the SFP module's labeling or accompanying documentation will denote its mode—look for "SM" indicating single mode or "MM" representing multimode.

  • Connector Color Examination: Single mode connectors generally appear blue, and multimode ones can be beige, black, or gray. This approach, however, is not foolproof since connector colors are not standard.

  • Fiber Core Size: Single mode fibers have a smaller core (about 9 microns) than multimode fibers (approximately 50 or 62.5 microns). With the right equipment, like a microscope, you may be able to measure the fiber's core diameter inside the module.

  • Manufacturer Inquiry: Contact the SFP module's producer with the model number or other pertinent data to have them verify your module's type.

Despite these methods, the nuances and specific variations of SFP modules mean that they may not always yield complete accuracy. Experts and professionals, equipped with appropriate expertise and instruments, can authenticate the SFP module type with certainty and guide you accordingly.

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