WTD RTXM139-400 SFP Transceiver

The WTD RTXM139-400 is a hot-pluggable SFP (Small Form-factor Pluggable) optical transceiver module designed for 155 Mbps SDH/SONET and PDH applications. It provides a single bidirectional optical interface operating at the nominal line rate of 155.52 Mbit/s (STM-1/OC-3).This module operates at a nominal wavelength of 1310 nm using a Fabry-Perot (FP) laser transmitter and a PIN photodiode receiver. It is optimized for single-mode fiber (SMF 9/125 µm) with a typical transmission distance of up to 15 km. The optical link budget supports reliable performance with low bit error rates (better than 10⁻¹²) over the specified reach. Transmitter average output power is typically in the range of -15 dBm to -8 dBm, while receiver sensitivity reaches down to -28 dBm or better.

The RTXM139-400 complies with the SFP MSA and relevant ITU-T G.957 / Telcordia standards for STM-1 IR-1 / S-1.1 interfaces. It supports framed SDH STM-1 and SONET OC-3 signals, including section, line, and path overhead processing when installed in a compatible host platform. Digital diagnostic monitoring (DDM) is available in this series, providing real-time access to optical power, temperature, and voltage parameters via the I²C interface.

Optical connectivity is realized through a duplex LC connector. Key operational features include Loss of Signal (LOS) detection and assertion, automatic laser shutdown (ALS) for Class 1 eye safety compliance, and hot-swap support. The module uses the standard 20-pin SFP electrical interface with a single +3.3 V power supply and low power consumption (typically below 1 W), making it suitable for high-density port configurations.

Environmental specifications include a commercial operating temperature range of -10°C to +70°C, high humidity tolerance, and built-in ESD protection. This SFP transceiver is primarily used for intermediate-reach 155 Mbps optical links in SDH/SONET add-drop multiplexers, PDH equipment, or as a tributary interface in multiservice transport platforms.

The module integrates seamlessly with network management systems for remote monitoring. Installation requires standard fiber optic cleaning procedures, correct Tx/Rx fiber polarity, and adherence to minimum bend radius guidelines for duplex LC patch cords. The WTD RTXM139-400 offers a reliable, cost-effective solution for 155 Mbit/s optical transport over single-mode fiber up to 15 km.