Improvement of transmission efficiency in microwave photonic links using EDFA

Photonics have long been viewed as an enabling technology that extends the sensing and signal processing performances of Radio Frequency (RF) remoting systems such as radar and electronic-warfare because of its inherent advantages in multi-octave operating frequencies, broad instantaneous bandwidth, low transmission loss, and good phase linearity. In order to improve the efficiency of the analog optical transmitter during electronic-to-optical conversion, an Erbium-Doped Fiber Amplifier (EDFA) combing with a low-bias modulator in an external intensity modulation direct detection link is applied. According to our analysis, the RF gain reduces linearly with modulator’s optical power output when the bias becomes close to its minimum. Thus, the gain provided by the EDFA to the optical signal was transferred to increase RF transmission efficiency. Experimental results indicated that the RF gain improved by 13.5 dB compared to that of conventional quadrature bias point transmissions. Meanwhile, a small penalty is introduced to system noise. Most importantly, this can be achieved by using off-the-shelf devices, which can drastically reduce the system’s cost. Finally, the proposed scheme can be widely used in electronic information equipment.