Speaker
Description
QTRx is an optical transceiver for particle physics experiments. The transmitters, each at 10 Gbps, are based on QLDD and 1x4 VCSEL array. The receivers, with data rates between 2.56 Gbps and 10 Gbps, are based on QTIA and 1x4 photodiode array, GaAs or InGaAs. QTRx is 20 mm × 10 mm × 5 mm and couples to an MT fiber connector. Preliminary tests indicate that QTRx meets design data rates with a power of 124 mW per Tx channel at 10 Gbps and 72 mW per Rx channel at 2.56 Gbps. More tests, including irradiation, will be carried out.
Summary (500 words)
QTRx is a 4-Tx, and 4-Rx optical transceiver developed for particle physics experiments. The Tx channels, each at 10 Gbps, are based on QLDD (quad laser diode driver), an ASIC resulting from previous developments of cpVLAD [1], and a 1x4 VCSEL array. The Rx channels are based on QTIA (quad transimpedance and limiting amplifier) and a 1x4 photodiode (PD) array of either GaAs or InGaAs. QTIA is optimized for operations at 2.56 and 10 Gbps per channel. Each channel of QLDD has a charge pump to address the possible increase of VCSEL forward voltage in radiation. QTIA is at the R&D stage with different PD biasing structures in each channel to study options for mitigating radiation-induced degradation in PDs. Details about QTIA are reported separately. Each Tx or Rx channel can be disabled via I2C block to save power. Both dies of QLDD and QTIA are 2 mm × 2 mm, fabricated in a 65 nm CMOS technology.
QTRx is 20 mm (L) × 10 mm (W) × 5 mm (H) and couples to an MT fiber connector. The electrical interface is a 40-pin connector for the moment and may be changed in the future. All components of QTRx are on one side of the PCB, leaving the other side to be coupled to cooling plates if needed.
The preliminary tests indicate that QTRx meets design data rates. The Tx optical eye has an RMS jitter of 4 ps. The rise and fall times are around 35 ps. The preliminary sensitivity of the receiver -17 dBm of the input optical power operating at 2.56 Gbps. The electric power consumption is 124 mW per Tx channel at 10 Gbps and 72 mW per Rx at 2.56 Gbps. A full set of evaluations, including performance in radiation, are planned for the coming months. We will present the results we have at the workshop.
Reference:
[1] Huang, X., D. Gong, D. Guo, S. Hou, G. Huang, S. Kulis, C. Liu et al. "A novel quad-channel 10 Gbps CMOS VCSEL array driver with integrated charge pumps." Journal of Instrumentation 15, no. 12 (2020): T12004.
