The system has six major components:
1. Laser source --> probably out of an SFP Port
2. Coupler
3. Photodiode
4. fiber optical cable
5. sensor head (fiber optical cable without a connector on the sensor head side)
6. Arduino as the microcontroller

All components are connceted via an LC connectors and adapters.

The pictures are from the SFP Port tear down:

Chips frontside:
- HE24C64: didn't find anything about that, but it looks like a ROM Chip

- TR3 K (the K is probably the date code): it looks exactly like the power mosfet NTR4503N from ON Semiconductors

and on the backside the chip is a

MYSON CENTURY CS6721 (2.5GBPS Post Amplifier and 1.25GBPS LD Driver with MCU).