Design and Verification of a 53-Gb/s PAM-4 Cooled DFB-LD TOSA Employing Cost-Effective TO-CAN Package

This article proposes a 53-Gb/s four-level pulse amplitude modulation (PAM-4) transmitter optical sub-assembly (TOSA) employing a cost-effective TO-CAN coaxial package. A distributed feedback (DFB) laser diode (LD), a monitoring photo-diode, a thermoelectric cooler (TEC), and a thermistor are integrated into a 7-pin commercial TO-56 TO-CAN package. The high-frequency characteristics of the entire TO-56 TO-CAN package, including the TO-56 header and LD submount, were simulated through a three-dimensional full-wave electromagnetic simulator; the resonance-free transmission bandwidth was over 30 GHz, and the reflection loss was below −10 dB within 19.55 GHz. The cooled O-band TO-56 TO-CAN DFB-LD TOSA had been realized, and its performance was measured using a self-designed evaluation board (EVB). The insertion loss of the EVB was simulated, and its bandwidth was 45.7 GHz. Using the TO-56 TO-CAN DFB-LD TOSA and EVB and setting the TEC temperature at 25 °C, the 53-Gb/s PAM-4 optical eye diagram was measured. Through a 15-tap equalizer, the extinction ratio of the 53-Gb/s PAM-4 optical eye diagram was 4.51 dB, the transmitter dispersion eye closure quaternary was 2.72 dB, and the optical modulation amplitude was 1.79 dBm. This cooled TO-56 TO-CAN DFB-LD TOSA with a TEC suits local area network - wavelength division multiplexing applications.