Overview:

It sounds like you're describing a 1.25Gbps Single Fiber Bi-Directional (BiDi) SFP Optical Transceiver that operates over a single strand of fiber using wavelength-division multiplexing (WDM). These transceivers are commonly used in Ethernet, SDH (Synchronous Digital Hierarchy), and SONET (Synchronous Optical Networking) networks.

Key Features:

• Transmission Distance: Starting from 20km 
• Single Fiber BiDi Operation: Uses a single LC or SC connector, transmitting and receiving on different wavelengths.
• Low Power Consumption: Efficient power usage helps in heat management and long-term operation.
• Compact Size: SFP form factor allows easy installation and hot-swapping.
• High Reliability: Designed for stable performance with low bit error rates (BER).
• Wide Temperature Range: Suitable for both commercial (0°C to 70°C) and industrial (-40°C to 85°C) environments.

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Common Wavelength Pairs for BiDi SFP Modules:

• Tx: 1310nm / Rx: 1550nm
• Tx: 1490nm / Rx: 1550nm
• Tx: 1550nm / Rx: 1310nm

Applications:

• Gigabit Ethernet (1.25Gbps)
• SDH/SONET Networks
• FTTx (Fiber to the X) Deployments
• Metro and Access Networks
• Industrial & Enterprise Network Backbones