ZyXel 1.25G BIDI WDM SFP Module 10-20KM - Reliable Single LC Link

In this review of the ZyXel 1.25G BIDI WDM SFP Module, the bottom line is simple: it is best for network technicians and small IT teams who need a cost effective, carrier-class replacement for vendor SFPs that supports bidirectional links over a single LC fiber. The reviewer found the module delivered the advertised 1.25Gbps SFP Bidi performance up to 20km and worked reliably in multiple switch brands thanks to Jeirdus compatibility testing, making it a practical choice when a direct, space-saving simplex LC connection is required.

Key Features

• Bidirectional 1.25Gbps: Supports both 1000BASE-BX-U and 1000BASE-BX-D protocols so a single module handles up and down links on one fiber.
• Simplex LC Connection: Uses a single LC connector which reduces fiber cabling complexity and suits duplex-constrained installations.
• Dual Wavelengths: Offers TX1310nm/RX1550nm or TX1550nm/RX1310nm configurations to match upstream and downstream requirements.
• Long Reach: Rated to work up to 20km, which covers most campus, metro and access applications without signal repeaters.
• Vendor Compatibility: Jeirdus compatibility lab ensures the transceiver meets coding requirements for popular switch brands, improving out-of-box interoperability.
• Quality and Support: Built from 100% new materials with CE and FCC compliance and a three year replacement plus lifetime warranty for peace of mind.

Who It's For

The module is aimed at network administrators, telecom technicians, and small data center teams that need a drop-in, cost effective replacement for branded Zyxel and compatible SFP BIDI modules. It is especially useful where single-fiber routing or limited fiber ports make a simplex LC transceiver the preferred option.

Those who should look elsewhere include users needing multi-rate SFP+ higher than 1.25Gbps or links longer than 20km, and buyers who require manufacturer-specific firmware features not supported by third-party compatible transceivers.

Pros & Cons

Pros

• Proven 1.25Gbps bidi performance that supports both BX-U and BX-D in standard networks.
• Simplex LC design reduces fiber cabling and simplifies installations in constrained spaces.
• Individually tested modules from a compatibility lab improve interoperability with major switch brands.
• Quality controls and CE/FCC compliance plus a three year replacement policy provide good value.

Cons

• Not suitable for speeds above 1.25Gbps, so it will not replace SFP+ or faster optics.
• Limited to the specified wavelengths and reach, so very long haul or nonstandard wavelengths are not supported.

Specifications

Form Factor	SFP Bidi Transceiver
Data Rate	1.25Gbps
Connector	Single LC (simplex)
Wavelength	Up: TX1310nm/RX1550nm or Down: TX1550nm/RX1310nm
Reach	Up to 20km
Standards	1000BASE-BX-U and 1000BASE-BX-D
Compliance	CE, FCC; 100% new materials

Our Verdict

The ZyXel 1.25G BIDI WDM SFP Module is a practical, value-oriented option for technicians who need reliable bidirectional single-fiber links up to 20km. With vendor compatibility testing, individual unit validation, and a multi-year replacement policy, it is a sensible choice for replacing branded transceivers where 1.25Gbps capacity and simplex LC are required.

Frequently Asked Questions

Will this module work in non-Zyxel switches?
Yes. Jeirdus performs compatibility testing to meet coding requirements for various brands and the module is compatible with many popular switches.

What distance can I expect?
The transceiver is rated to reach up to 20km over single-mode fiber when used with the appropriate paired wavelength module.

Is this module covered by warranty?
Yes. It is built with 100% new materials, meets CE and FCC standards, and comes with a three year replacement policy plus lifetime warranty.