GBT20, a 20.48 Gbps PAM4 optical transmitter module for particle physics experiments

Abstract

We present a pluggable radiation-tolerant 4-level Pulse-Amplitude-Modulation (PAM4) optical transmitter module called GBT20 (Giga-Bit Transmitter at 20 Gbps) for particle-physics experiments. GBT20 has an OSFP or firefly connector to input 16 bit data each at 1.28 Gbps. The GBT20 drives a VCSEL die with an LC lens or a VCSEL TOSA and interfaces an optical fiber with a standard LC connector. The minimum module, including the host connector, occupies 41 mm × 13 mm × 6 mm. At 20.48 Gbps, the minimum Transmitter Dispersion Eye Closure Quaternary (TDECQ) is around 0.7 dB. The power consumption is around 164 mW in the low-power mode. The SEE cross-section is below 7.5 × 10−14 cm2. No significant performance degrades after a TID of 5.4 kGy.

Design and verification of DFE re-decision algorithm for PAM6 high-speed transceiver based on FPGA

“…When the demodulation module encounters a combination of four gray areas, it will be assigned to any white area adjacent to the gray area by default. For example, when (5,5) is encountered, the adjacent combinations are (5, 3), (3,5), and (3,3). The demodulation default is set by the user.…”

“…The demodulation default is set by the user. Suppose the user chooses (5,3), which is 10110. This means that all (5, 5) will be demodulated as (5,3).…”

“…Suppose the user chooses (5,3), which is 10110. This means that all (5, 5) will be demodulated as (5,3). However, it is also possible that (3, 5) becomes (5,5).…”

“…In high-energy physics (HEP) experiments, the data transmission rate from the detector to the back-end stages is increasing [1][2][3][4]. In this field, 4-level pulse-amplitude-modulation (PAM4) is a commonly used data modulation scheme [5][6][7]. However, as data rates become increasingly faster, the need for bandwidth increases.…”

“…For instance, two consecutive "5" in the received PAM6 symbol "-3, 5, 5, 1, 5, 5" appear twice, but only the second group is a known invalid condition, as described in this paper. The above PAM6 symbol combinations are (-3, 5), (5,1), and (5,5).…”