The **HFE3524-3DT2-R** is a high-performance **Fiber Optic Transmitter** (Optical Sub-Assembly) manufactured by Finisar (now part of II-VI Incorporated). It is designed for high-speed data communications, specifically for Gigabit Ethernet and Fibre Channel applications. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Component Type** | VCSEL (Vertical Cavity Surface Emitting Laser) | | **Operating Wavelength** | 850 nm | | **Data Rate** | Up to 4.25 Gbps | | **Package Style** | LC TOSA (Transmitter Optical Sub-Assembly) | | **Optical Power** | -9 to -3 dBm (typical) | | **Input Interface** | Differential 100 Ohm | | **Operating Temperature** | -40°C to +85°C (Industrial Grade) | --- ### 2. Core Electronic Components The device is not just a laser; it contains several integrated electronic subsystems to ensure stable performance: #### A. The VCSEL Diode The heart of the component is a high-speed **850nm VCSEL**. Unlike traditional edge-emitting lasers, the VCSEL emits light vertically from its top surface, offering lower threshold currents and higher reliability. #### B. Monitoring Photodiode (MPD) Inside the TOSA, a back-facet monitor photodiode is integrated. * **Function:** It senses a small portion of the laser output. * **Purpose:** It provides a feedback signal to the external laser driver circuit to implement **Automatic Power Control (APC)**, ensuring the light output remains constant despite temperature fluctuations. #### C. Electrical Interface * **Differential Driving:** The part uses a differential input to minimize Electromagnetic Interference (EMI) and ensure signal integrity at Gigahertz speeds. * **Flex Circuit/Pins:** Depending on the specific sub-variant, it typically connects via a flex circuit or high-speed pins designed to minimize parasitic inductance. --- ### 3. Structural Features * **LC Connector Interface:** The "3DT2" designation refers to the mechanical housing, which features an LC-type receptacle for fiber optic patch cables. * **Integrated Lens:** It includes a precision-aligned ball lens or aspheric lens to focus the VCSEL output into the core of a Multi-Mode Fiber (MMF). ### 4. Typical Applications * **SFP Transceivers:** Used as the light-source component inside Small Form-factor Pluggable modules. * **Storage Area Networks (SAN):** Supporting 1x/2x/4x Fibre Channel. * **Ethernet:** 1000Base-SX high-speed backplanes. ---