How to get the optical module wiring

Optical module wiring sequences ensure proper signal flow and prevent damage, with SFP modules using sequenced pin connections and MPO patch cords following Type A, B, or C standards.

SFP Module Wiring Sequence

SFP transceivers use a sequenced mating of connector pins to protect the module and host system:

• First mate: Ground contacts
• Second mate: Power supply pins (Vcc)
• Third mate: Data signal pins (TX/RX) This sequence prevents electrical damage and signal interference during insertion. Key pins include TX+, TX-, RX+, RX- for differential signals, TX_DIS to disable the transmitter, TX_FAULT for fault detection, and MOD_DEF(0-2) for module identification and I²C communication . Differential signals are AC-coupled inside the module, so the host board does not require additional coupling capacitors.

MPO Patch Cord Wiring Sequence

For parallel transmission optical modules (e.g., 40G-SR4, 100G-SR4), MPO patch cords follow TIA-568 standards with three main types:

• Type A (Key up–Key down): Straight-through fiber bundle; fiber positions are identical at both ends.
• Type B (Key up–Key up): Full-cross fiber bundle; fiber positions are completely reversed at both ends.
• Type C (Key up–Key down, pair-wise cross): Each adjacent fiber pair is reversed at one end relative to the other . MPO adapters are used to connect patch cords and come in Type A (key up–key down) and Type B (key up–key up) configurations. Correct selection ensures proper polarity and signal alignment between transmitters and receivers.

Practical Connection Guidelines

1. Verify module type: Ensure the SFP or parallel module matches the intended data rate and fiber type (single-mode or multimode).
2. Check pin sequence: For SFP modules, confirm ground, power, and signal pins are correctly aligned.
3. Select MPO patch cord type: Use Type A for straight-through connections, Type B for reversed connections, and Type C for pair-wise cross connections.
4. Use compatible adapters: Match MPO adapter type to patch cord type to maintain correct polarity.
5. Test signal integrity: After installation, verify optical power levels and link performance to ensure proper wiring and module operation . Following these wiring sequences ensures reliable optical communication, prevents module damage, and maintains signal integrity in high-speed networks.