Compact Hybrid-Integrated 100-Gb/s TOSA Using EADFB Laser Array and AWG Multiplexer

We have developed a compact hybrid-integrated four-lane $\times 25.8$ Gb/s transmitter optical sub-assembly (TOSA) for a 100 Gb/s transceiver for 40-km transmission. The TOSA has a simple configuration in which a four-channel electroabsorption modulator integrated distributed feedback (EADFB) laser array is directly attached to the input waveguide end-faces of a silica-based arrayed waveguide grating (AWG) multiplexer. We integrated a lateral tapered spot-size converter for the EADFB laser to achieve a high optical butt coupling efficiency between the EADFB lasers array and the AWG multiplexer. We confirmed that the TOSA, which is $19.9~\text {mm} \,\times \, 6~\text {mm} \,\times \, 5.8$ mm, achieved error-free operation for a 40-km transmission with a high average optical output power of over 0.3 dBm at an operating temperature of 55 °C.

I. Introduction

Highly compact and cost-effective optical transceivers are needed to deal with the exponential growth in data traffic generated in telecommunication networks. 100-Gbit/s Ethernet (100GbE), standardized as IEEE 802.3ba [1], has a long reach specifications as regards its use with single-mode fiber (SMF), namely 100GBASE-LR4 for 10-km and 100GBASE-ER4 for 40-km. The specifications employ a multi-lane configuration that has four 25.78125 Gbit/s lanes with local area network wavelength division multiplexing (LAN-WDM), which is assigned a wavelength channel spacing of 800 GHz in the 1.3- wavelength band. To further reduce both the size and power consumption of the 100GbE transceiver, a CFP4 transceiver has been under discussion in relation to the centum form-factor pluggable (CFP) multi-source agreement (MSA) [2]. To obtain a multi-lane transmitter optical sub-assembly (TOSA) for a CFP4 transceiver that satisfies 100GBASE-ER4, it is important to pursue TOSA miniaturization while realizing an average optical output power ( of over −1.5 dBm at a minimum dynamic extinction ratio (DER) of 8 dB to keep an optical modulation amplitude (OMA) of over 0.1 dBm.