The **FNS-155-R** is a high-performance, single-mode optical transceiver module, typically utilizing the **SFP (Small Form-factor Pluggable)** standard. It is designed for SDH/SONET applications, specifically at the OC-3/STM-1 rate (155 Mbps). Below is a breakdown of its core electronic components and technical specifications. --- ## 1. Core Electronic Components The device operates by converting electrical signals into optical pulses and vice versa. The following internal components facilitate this process: | Component | Function | | :--- | :--- | | **LD (Laser Diode) Driver** | An IC that modulates the laser diode to convert electrical data into light pulses. | | **FP-LD (Fabry-Perot Laser)** | The light source (transmitter) that generates the optical signal at a 1310nm wavelength. | | **TIA (Transimpedance Amp)** | Converts the low-level current from the optical receiver into a usable voltage signal. | | **Limiting Amplifier** | Stabilizes the electrical signal from the TIA to ensure clean high/low (0 and 1) logic levels. | | **EEPROM** | A memory chip containing serial ID information and manufacturer data (MSA compliant). | --- ## 2. Technical Specifications The "R" in the part number often signifies a specific distance rating (usually "Intermediate Reach" or "Long Reach"). ### Optical & Electrical Characteristics * **Data Rate:** 155 Mbps (Synchronous Digital Hierarchy). * **Wavelength:** 1310 nm (Single-mode). * **Distance:** Typically up to 15km or 20km (standard for "R" or "Intermediate" variants). * **Supply Voltage:** 3.3V (Standard for SFP modules). * **Connector Type:** LC Duplex. --- ## 3. Pin Functionality (SFP Standard) The FNS-155-R uses a 20-pin gold-finger connector. Key pin functions include: 1. **VeeT / VeeR:** Grounding for the transmitter and receiver. 2. **TX_Fault:** An output indicating if the laser is malfunctioning. 3. **TX_Disable:** An input to turn off the laser for safety or power saving. 4. **MOD-DEF (0-2):** The 2-wire serial interface for the EEPROM data. 5. **RD+/- & TD+/-:** Differential pairs for the high-speed data transfer. --- ## 4. Operational Diagram ```mermaid graph LR A[Electrical Input] --> B[LD Driver] B --> C[1310nm Laser] C --> D{Fiber Optic} D --> E[PIN Photodiode] E --> F[TIA/Limiting Amp] F --> G[Electrical Output] ``` ---