The NP-2000 erbium-doped fiber amplifier (EDFA) optical gain block from Nuphoton Technologies is an efficient fiber pumped with 980-nm semiconductor laser pumps. Wavelength combiners combine the pump laser and the incoming signal into the erbium-doped fiber for signal amplification. Input and output isolation makes the EDFA insensitive to the unwanted reflections from optical connectors. Photodiodes mounted inside the pump module sense and monitor the pump's output power. The pump module has a TE cooler and a temperature sensor.