A single-mode fiber can be used with one optical module, but the configuration depends on whether the module is single-fiber (BiDi) or dual-fiber.

Single-Mode Fiber Overview

Single-mode (SM) fiber has a small core (typically 9 µm) that allows light to travel in a single propagation mode, minimizing modal dispersion and enabling long-distance transmission with low signal loss . It is commonly used in long-haul, carrier, and metropolitan networks .

Optical Module Configurations

Optical modules can be designed for either single-core (1-core) or dual-core (2-core) fibers:

• 1-core (single-channel) modules: Use a single fiber core for data transmission. This can be implemented as a BiDi (bidirectional) module, where one fiber carries both transmit and receive signals, effectively allowing a single fiber to serve one optical module .
• 2-core (dual-channel) modules: Use two fibers, one for transmitting and one for receiving. This is the traditional setup for most optical links and is easier to configure for stable communication [4^].

Practical Implications

• Single-mode single-fiber modules are ideal when fiber availability is limited or when saving space and cost is important. They require precise optics to handle bidirectional signals on one fiber .
• Dual-fiber single-mode modules are more common in long-distance networks, providing straightforward setup and reliable performance .
• Multi-mode fibers, by contrast, are typically used for short distances and can also be configured as single-core or dual-core, but they have larger cores and support multiple light paths, which limits their reach compared to single-mode fibers .

Summary

Yes, a single-mode fiber can be used for one optical module, particularly in single-fiber (BiDi) configurations. However, many single-mode modules still use two fibers for separate transmit and receive channels. The choice depends on network design, distance, and cost considerations .