## Overview: NX8564LE820 The **NX8564LE820** is a high-performance, 1310 nm Distributed Feedback (DFB) laser diode module. It is specifically designed for fiber-optic communication systems, particularly for high-speed data transmission over Long-Reach (LR) networks. --- ### 1. Key Technical Specifications The following table outlines the core electronic and optical characteristics of the device: | Parameter | Specification (Typical) | Unit | | :--- | :--- | :--- | | **Wavelength** | 1310 | nm | | **Output Power** | 2.0 | mW | | **Data Rate** | Up to 2.5 (OC-48/STM-16) | Gbps | | **Laser Type** | MQW-DFB (Multiple Quantum Well) | - | | **Forward Current** | 15 - 35 | mA | | **Operating Temp** | -20 to +85 | °C | --- ### 2. Internal Electronic Components The module is not just a laser; it contains several integrated components within its housing (typically a TOSA or specialized butterfly package) to ensure stability: 1. **DFB Laser Diode**: The light source. Unlike standard FP lasers, the DFB structure uses a "grating" to force the laser to emit at a single, precise frequency, reducing chromatic dispersion. 2. **Monitor Photodiode (MPD)**: Integrated behind the laser to measure back-facet light. This allows the system to use an **Automatic Power Control (APC)** circuit to adjust the bias current as the laser ages or heats up. 3. **Optical Isolator**: Often included to prevent reflected light from traveling back into the laser cavity, which would cause "relative intensity noise" (RIN) and signal instability. 4. **Thermoelectric Cooler (TEC)**: (Model dependent) Some variants include a TEC and a Thermistor to maintain a constant internal temperature, ensuring wavelength stability. --- ### 3. Application Use-Cases The NX8564 series is primarily used in the following electronic infrastructures: * **SONET/SDH Networks**: OC-48 and STM-16 transmission. * **Fiber-to-the-Home (FTTH)**: High-speed optical line terminals. * **Metropolitan Area Networks (MAN)**: Connecting data centers over distances up to 40km without amplification. * **Test Equipment**: Light sources for optical power meters and fiber testers. --- ### 4. Circuit Implementation Tips When designing a PCB for this part, consider the following: * **Impedance Matching**: Ensure 25Ω or 50Ω matching (depending on the package) to prevent signal reflection at 2.5 Gbps. * **ESD Sensitivity**: Laser diodes are extremely sensitive to static discharge. Always use ESD-safe handling procedures. * **Current Limiting**: Never exceed the maximum forward current (I_f) specified in the datasheet, as this will lead to immediate catastrophic optical damage (COD).