‌How Do Optical Modules Achieve Single-fiber Bidirectional Transmission?--ETU-LINK

‌How do optical modules achieve single-fiber bidirectional transmission?

May 28. 2026

Ⅰ. "Dual-channel" transmission and reception, without interference.

Bidirectional over Single Fiber ( BiDi ) means that data transmission and reception can be completed simultaneously within a single optical fiber, unlike ordinary optical fibers which use two separate wires for transmission and reception. The core principle of this technology is the combination of wavelength multiplexing and transmit/receive separation, which can be elaborated from the following three aspects:

1.Wavelength-differentiated transmission and reception: The two ends of the communication use different wavelengths in a symmetrical and opposite direction for transmission and reception (e.g., A transmits at 1310nm and receives at 1550nm, while B does the opposite), to achieve interference-free bidirectional signal transmission.

2.Core Component: WDM Coupler (wavelength division multiplexer): As a key component, it sends optical signals of different wavelengths into a single optical fiber for transmission by multiplexing, and the receiving end then demultiplexes the signals to the corresponding modules to complete bidirectional transmission.

3.Technical Essence: Compared with the traditional dual-fiber solution, this technology reduces the amount of optical fiber used by 50% and improves resource utilization by combining single fiber with dual wavelengths without affecting transmission performance.

Ⅱ.Optical Module Core Series and Application Scenarios

Rate	Product Models	Description and application scenarios	Wavelength Pairing (TX/RX)
1.25G	EB3512-3D/10D/20D/40D	1.25G SFP optical module, supporting different transmission distances of 3/10/20/40km, adaptable to general access scenarios, with DDM monitoring function.	1310nm/1550nm
1.25G	EB5312-3D/10D/20D/40D		1550nm/1310nm
10G	EB23X-10D/20D/40D/60D	10G SFP+ optical modules, covering transmission distances of 10-60km, suitable for campus backbone and metropolitan area networks, supporting hot-swapping and DDM functions.	1270nm/1330nm
10G	EB32X-10D/20D/40D/60D		1330nm/1270nm
25G	EB232X-10D/40D	25G SFP28 optical module, 10/40km transmission distance, suitable for 5G fronthaul and data center scenarios, supports hot-swapping and DDM monitoring.	1270nm/1330nm
25G	EB322X-10D/40D		1330nm/1270nm
40G	EB894X-01D	40G QSFP+ optical module, short-distance 150m version, multi-mode design, specifically designed for data center interconnection and backbone expansion scenarios.	Tx850nm/Rx900nm ↔ Tx900nm/Rx850nm
100G	EB23Y-10D	100G QSFP28 high-speed optical module, 10km short-to-medium distance version, suitable for data centers and short-to-medium distance interconnection, supports hot-swapping and DDM monitoring.	1270nm/1330nm
100G	EB32Y-10D		1330nm/1270nm

The optical communication market is set to make a significant impact in 2026, with ETU-LINK 100G BIDI series products making a powerful debut. Precisely covering transmission needs across 10km, 20km, 40km, and 80km ranges, these products have become a benchmark product in the industry, boasting superior performance, stable quality, and exceptional cost-effectiveness. From data center interconnection to long-distance transmission, from engineering deployment to daily operation, products must be used in pairs: the wavelengths at both ends must be complementary (A transmits at 1310nm/receives at 1550nm, B must transmit at 1550nm/receive at 1310nm); single-end communication is impossible.

Not all wavelengths can be paired: standard wavelength combinations must be , otherwise the signal cannot be separated.

Ⅲ.Summarize

Bidirectional single-fiber (BiDi) transmission technology is a core technology in the field of optical communication that combines practicality and economy. It achieves bidirectional signal transmission over a single fiber through wavelength splitting and single-fiber multiplexing, adaptable to various speeds such as gigabit and 10-gigabit speeds and transmission scenarios ranging from 10 to 100 kilometers. This technology is widely used in access networks, 5G base stations, security monitoring, and other fields, effectively reducing fiber usage and deployment costs while improving transmission efficiency and fiber resource utilization. It is a key solution for cost reduction and efficiency improvement in optical communication engineering.

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