The **FCLM635S20LD6** is a high-performance optoelectronic component, specifically a **Coaxial Pigtailed Laser Diode Module**. These modules are designed for precision applications requiring a stable light source coupled directly into a fiber optic cable. ### 1. Technical Specifications The following table highlights the primary electronic and optical characteristics of the FCLM635S20LD6: | Parameter | Typical Value | Unit | | :--- | :--- | :--- | | **Peak Wavelength** | 635 (±5) | nm (Visible Red) | | **Optical Output Power** | 20 | mW | | **Operating Current ($I_{op}$)** | 60 - 90 | mA | | **Threshold Current ($I_{th}$)** | 35 - 50 | mA | | **Operating Voltage ($V_{op}$)** | 2.2 - 2.6 | V | | **Fiber Type** | Single Mode (SM) / Multi-Mode (MM) | - | | **Operating Temperature** | -10 to +50 | °C | --- ### 2. Core Electronic Components The module is not just a single part but an assembly consisting of several critical electronic elements: #### A. Laser Diode (LD) Chip The heart of the module is a semiconductor laser chip based on AlGaInP technology. It converts electrical energy into coherent red light through stimulated emission. #### B. Monitor Photodiode (PD) Most FCLM series modules include an internal silicon photodiode. This PD captures a small fraction of the laser light to: * Provide feedback to the driver circuit. * Enable **Automatic Power Control (APC)** to keep output power constant despite temperature fluctuations. #### C. Built-in Thermistor (Optional in some variants) To ensure wavelength stability, some high-end pigtail modules include a NTC thermistor to monitor the internal temperature of the diode junction. --- ### 3. Pin Configuration & Connection Typically, these modules use a 3-pin or 4-pin TO-can style header inside the coaxial housing. The standard wiring usually follows one of these logic patterns: * **Pin 1:** Laser Diode Cathode (LD-) * **Pin 2:** Common (LD Anode + PD Cathode) * **Pin 3:** Photodiode Anode (PD+) > **Caution:** Laser diodes are extremely sensitive to **Electrostatic Discharge (ESD)**. Always use a grounded wrist strap and an ESD-safe soldering iron when handling these parts. --- ### 4. Key Applications Because of its pigtail design (which eliminates the need for external alignment lenses), it is used in: 1. **Fiber Optic Testing:** As a visible light source for fault locators (VFL). 2. **Medical Instrumentation:** Laser therapy or aiming beams for surgical lasers. 3. **Industrial Alignment:** Precise positioning using fiber-guided red light. 4. **Sensors:** Used in particle counting or interferometry.