Multimode 850nm series optical module fiber patch cord selection method

1. Classification of Multimode 850nm Series Optical Modules

• Classified by Package Type

The mainstream packages for multimode 850nm products in the current market are SFP (Single-Fiber Bidirectional, single transmit and single receive mechanism) and QSFP (multi-transmit and multi-receive, multi-channel optical parallel transmission). Other packages such as GBIC/X2/XENPAK are rarely used, while the XFP package is being rapidly replaced.

For SFP package multimode products, the main models in market demand are SFP-GE-SX, SFP-10GB-SR, and SFP28-25GB-SR. For QSFP package multimode products, the mainstream models are QSFP-40GB-SR4 and QSFP28-100GB-SR4.

• Classified by Transmission Rate

Current multimode optical modules on the market cover a rate range from 1G to 400G, meeting the short-distance transmission needs of various application scenarios.

2. General Rules for Selecting Multimode Fiber Patch Cords

Unlike single-mode modules (whose transmission is mainly limited by fiber link optical attenuation), the transmission distance of multimode modules is generally not constrained by optical circuit attenuation. Instead, it is limited by the module’s own modal characteristics and the fiber’s modal bandwidth.

Single-channel 1G Multimode Modules: The transmission distance can reach 300m over 62.5/125μm multimode fiber and 550m over 50/125μm multimode fiber.

Single-channel 10G Multimode Modules: Common models include SFP-10GB-SR, QSFP-40GB-SR4, and CFP2-100GB-SR10. Their transmission distance is further limited by fiber type, with specific ranges as shown in Table 1 (refer to IEEE Std 802.3-2015).

Table 1: Transmission Distance Specifications

Fiber	Minimum modal bandiwdth @850nm (MHz•km)	Operating range(m)
62.5 μm MMF	160	2 to 26
62.5 μm MMF	200	2 to 66
50 μm MMF	400	2 to 66
	500	2 to 82
	2000	2 to 300
	4700	2 to 400

Single-channel 25G Multimode Modules: Models such as SFP-25GB-SR, QSFP28-100GB-SR4, QSFP-DD 200GB-SR8, and 400GB-SR16 are all based on single-channel 25G mode. The transmission distance is 70m over OM3 multimode fiber, 100m over OM4 fiber, and better transmission performance is achieved over OM5 fiber.

• Requirements for Patch Cord Connector Types

SFP and QSFP multimode modules have different requirements for fiber patch cord connector forms:

SFP Multimode Modules: Commonly use dual LC connector patch cords, as shown in Figure 1.

Figure 1: Diagram of Dual LC Patch Cord Connector

QSFP Multimode Modules: Adopt parallel transmission of multiple optical signals with the same wavelength (SR4, SR8, SR16 indicate the number of parallel transmission channels), using MPO/MTP multiplexed fiber array connectors. The number of cores depends on the module’s channel count, as shown in Figure 2.