Low‐cost coaxial DFB LD transmitter optical subassembly for 25 Gb/s NRZ and 50 Gb/s PAM‐4 transmissions

Abstract

Here, a directly modulated coaxial distributed feedback (DFB) laser diode (LD) transmitter optical subassembly (TOSA) module is proposed for 25 Gb/s non-return-to-zero (NRZ) and 50 Gb/s four-level pulse amplitude modulation (PAM-4) transmissions. A low-cost TO-56 header was used in the DFB LD TOSA package. The high-frequency performance of the coaxial 1310 nm DFB LD TOSA module was simulated and analysed. The simulated frequency response can correspond with the measured result, and the 3 dB bandwidth was 19 GHz. In the back-to-back and 10 km signal mode fibre transmissions, 25 Gb/s NRZ and 50 Gb/s PAM-4 eye diagrams of the DFB LD TOSA were measured. Clear 25 Gb/s NRZ and 50 Gb/s PAM-4 eye openings can be observed. For 25 Gb/s NRZ transmissions, the received sensitivity was −11.8 dBm under a bit error rate (BER) of 10 −12 . For 50 Gb/s PAM-4 transmissions, the BER was estimated to be below the forward error correction threshold. The low-cost coaxial DFB LD TOSA is suitable in 100, 200, and 400 Gb/s transmissions.