HP J4858C ProCurve Gigabit SX-LC Mini-GBIC

The HP J4858C (also known as HP X121 1G SFP LC SX Transceiver) is a hot-pluggable Mini-GBIC (SFP) optical transceiver module designed for 1000BASE-SX Gigabit Ethernet applications. It operates at a nominal wavelength of 850 nm using a VCSEL (Vertical Cavity Surface Emitting Laser) transmitter and a PIN photodiode receiver. The module provides a full-duplex Gigabit Ethernet solution and complies with the IEEE 802.3z 1000BASE-SX standard and the SFP Multi-Source Agreement (MSA).This transceiver supports transmission distances up to 550 m over 50/125 µm multi-mode fiber (MMF) with 500 MHz·km modal bandwidth, or up to 220–275 m over 62.5/125 µm MMF depending on the fiber bandwidth. It features a duplex LC optical connector and is intended exclusively for multi-mode fiber applications. The electrical interface uses a standard 20-pin SFP connector with differential CML signals. The module operates from a single +3.3 V power supply with low power consumption, typically 0.4 W and maximum below 1 W.

Digital diagnostic monitoring (DDM/DOM) is supported on this model, providing real-time access via the two-wire I2C interface to parameters such as transmitted optical power, received optical power, laser bias current, supply voltage, and module temperature. The design meets IEEE 802.3z requirements for jitter tolerance, extinction ratio, and eye mask compliance. The J4858C is classified as a Class 1 laser product and complies with RoHS and EMC standards.

The transceiver is optimized for use in HP ProCurve and HPE networking equipment, including ProCurve switches and compatible third-party devices with SFP ports. It is ideal for short-reach Gigabit Ethernet connections within data centers, campus networks, and enterprise environments, such as intra-building or intra-rack links over multi-mode fiber infrastructure.

Installation is straightforward due to the hot-pluggable SFP form factor, allowing insertion or removal without powering down the host equipment. The module supports commercial operating temperatures from 0°C to +70°C and requires minimal airflow for thermal management. Proper cleaning and inspection of the duplex LC connectors are essential to prevent contamination and maintain optimal link performance.

During operation, the J4858C performs automatic link negotiation and provides calibrated digital diagnostic data where supported by the host device. Recommended fiber patch cables are duplex multi-mode LC-to-LC with OM2 or better fiber for maximum reach up to 550 m. The module integrates with host management systems through standard SNMP or CLI for remote monitoring of optical parameters and link status.

This Gigabit SX SFP transceiver offers a reliable, standards-compliant solution for upgrading or expanding 1000 Mbps optical connectivity in HP ProCurve environments with short-reach multi-mode fiber links.