Quantum Dot Wafer for 10G PON Lasers

Today’s passive optical network (PON) equipment is mature and operators are on track for full deployment. However, to better support personalized subscriber services, PON optical access technologies are rapidly evolving towards higher speeds.

This evolution prompted IEEE’s 802.3av 10 Gb/s Ethernet PON (10G EPON) standardization kickoff in 2006. A similar effort by FSAN/ITU-T, designated NG-PON, will begin officially in 2009. Both standards are for 10 Gb/s downstream systems, despite fundamental system differences. They utilize upstream wavelengths of 1310 ± 50 nm for 1 Gb/s (GEPON and GPON compatibility) and 1270 ± 10 nm for higher speed, e.g., 2.5 or 10 Gb/s. The 10 Gb/s high speed upstream wavelength band, from 1260 nm to 1280 nm, is officially adopted for 10G EPON and expected for NG-PON as well.

The high speed, directly modulated upstream laser in the optical network unit (ONU) must be uncooled, inexpensive, and generally robust. 1270 nm is near the lower end of the spectrum accessible by InP-based quantum well (QW) lasers, but they are overly sensitive to operating temperature, and efficiency is limited by carrier confinement issues. In contrast, Innolume has demonstrated that lasers based on engineered InAs/GaAs quantum dot (QD) gain layers are optimal at this upstream 1270 nm wavelength, enabling the necessary temperature insensitivity, low threshold current, high efficiency, high speed, high power, and narrow bandwidth.

Innolume has successfully developed Quantum Dot technology for manufacturing temperature insensitive DFB lasers operating at 2.5 and 10 Gb/s with lasing wavelength around 1310nm. Specifications for these wafers and example of high-speed operation of laser diodes fabricated from them are shown here. Quantum Dot growth technology is easily adjustable to ensure superior performance for DFB lasers also at 1270 nm.