Transimpedance amplifiers boast improved sensitivity, dynamic range

The cost of optical network terminals (ONT) for deploying fiber-to-the-x multi-play services over fiber-access networks that use Gigabit Ethernet passive optical network (GEPON) and Gigabit PON (GPON) technology is set to fall further, according to Mindspeed Technologies Inc., which has deployed a new generation of high-sensitivity 1.25Gb/s and 2.5Gb/s transimpedance amplifiers (TIAs).

Mindspeed said its 2.5Gb/s M02025 and 1.25Gb/s M02028 improve optical sensitivity and dynamic range while adding key new features such as wide input dynamic range and support for various transmission distance requirements, including short-haul fiber-optic systems that require typical input overload of 4mA (peak to peak). They are also able to detect tiny small signals in a noisy environment such as in high-split-ratio PON networks. In Receiver Optical Sub Assembly (ROSA) applications, the M02025 TIA's typical sensitivity is better than -28dBm at 3Gb/s and better than -30dBm at 2.5Gb/s when used with a PIN diode. Performance with an avalanche photodiode exceeds -35dBm at 2.5Gb/s.

The TIAs, which both support multiple data rates, from 1.25Gb/s to 3Gb/s and from 100Mb/s to 1.25Gb/s for the M02025 and M02028, respectively, make the use of photodiode filtering caps and internal ROSA power supply decoupling caps unnecessary, thereby lowering the overall ROSA assembly costs. The company said the devices are designed with integrated average photodiode current outputs that support both PIN and APD-based photodiode monitoring with "excellent" accuracy. They also have on-die temperature sensors suitable for APD temperature monitoring implementations.

Hasnain Bajwa, senior vice president and general manager of Mindspeed's lightspeed connectivity solutions business unit, said that the TIAs, "when used with our highly integrated laser drivers, streamline the design of GPON and GEPON ONTs."