Laser radar device performing multi-stage amplification

A laser radar device comprising:

• a signal light source configured to output a first signal light;
• a pump light source configured to output a pump light;
• an optical coupler configured to receive the first signal light and the pump light;
• a pump optical fiber configured to transfer the pump light;
• a first signal optical fiber configured to transfer the first signal light;
• a first amplifier configured to receive and amplify the first signal light from the first signal optical fiber, wherein the amplified first signal light is input back to the optical coupler;
• a second signal optical fiber configured to receive and transfer a second signal light from the first amplifier, the second signal light being the amplified first signal light;
• a second amplifier configured to receive and amplify the second signal light from the second signal optical fiber, wherein the amplified second signal light is input back to the optical coupler;
• a third signal optical fiber configured to receive and transfer a third signal light from the second amplifier, the third signal light being the amplified second signal light;
• a third amplifier configured to receive and amplify the third signal light from the third signal optical fiber,
• wherein the optical coupler is connected to the first signal optical fiber, the second signal optical fiber, the third signal optical fiber, and the pump optical fiber, and configured to distribute the pump light to the first signal optical fiber, the second signal optical fiber, and the third signal optical fiber.