A low heat release cladding pump coupler

Few-mode erbium-doped fiber amplifiers (FM-EDFAs) have opened up the possibility of realizing the next generation of high-capacity, high-rate communication systems. However, the leakage of pump light during continuous operation of the FM-EDFA is likely to cause the temperature of the cladding pump coupler to be too high and thus destabilize the amplifier. In this work, a low heat release cladding pump coupler was designed and the corresponding FM-EDFA was constructed. The cladding pump coupler in the 8 h of continuous operation of the FM-EDFA is at 27.8 °C for maximum, 23.7 °C for minimum, and 26 °C for average temperatures, respectively, which are in a low-temperature safe transmission state. The FM-EDFA performance test was performed on this basis, and the results show that when the input pump power is 7 W, the maximum gain fluctuation of each mode of FM-EDFA at 1550 nm in 0∼8 h is only 1.5 dB, the gain of all modes is greater than 23 dB and the differential mode gain (DMG) is less than 2 dB. In addition, the FM-EDFA still has good performance in the C-band after 8 h of continuous operation. The gain for all modes is greater than 21 dB, DMG is less than 2 dB, and wavelength flatness is 3.6 dB. The low heat release cladding pump coupler is conducive to the stable amplification transmission of FM-EDFA, which is of great significance to achieving the upgrading and expansion of the communication system. •The maximum temperature of the cladding pump coupler was only 27.8 °C during 8 h of continuous operation.•Pump coupling efficiency up to 82%.•The gain of all modes of FM-EDFA basically stabilised without significant fluctuations during 8 h.•FM-EDFA has the characteristics of high gain, low DMG, and good wavelength flatness.