Modulator-Based, High Bandwidth Optical Links for HEP Experiments

TL;DR

This paper explores the development of small, high-bandwidth, radiation-hard optical links using light modulators as a promising alternative to VCSELs for high-energy physics experiments, demonstrating their performance and radiation resilience.

Contribution

It introduces a novel approach using various light modulators for high-speed optical links, with comprehensive testing and radiation hardness validation for potential use in HEP experiments.

Findings

Achieved 10 Gb/s data transmission with three types of modulators

Confirmed radiation hardness up to ~1012 protons/cm2 and 65 krad TID

Built a 40 Gb/s bi-directional link for 100m fiber runs

Abstract

As a concern with the reliability, bandwidth and mass of future optical links in LHC experiments, we are investigating CW lasers and light modulators as an alternative to VCSELs. These links will be particularly useful if they utilize light modulators which are very small, low power, high bandwidth, and are very radiation hard. We have constructed a test system with 3 such links, each operating at 10 Gb/s. We present the quality of these links (jitter, rise and fall time, BER) and eye mask margins (10GbE) for 3 different types of modulators: LiNbO3-based, InP-based, and Si-based. We present the results of radiation hardness measurements with up to ~1012 protons/cm2 and ~65 krad total ionizing dose (TID), confirming no single event effects (SEE) at 10 Gb/s with either of the 3 types of modulators. These optical links will be an integral part of intelligent tracking systems at various scales from coupled sensors through intra-module and off detector communication. We have used a Si-based photonic transceiver to build a complete 40 Gb/s bi-directional link (10 Gb/s in each of four fibers) for a 100m run and have characterized it to compare with standard VCSEL-based optical links. Some future developments of optical modulator-based high bandwidth optical readout systems, and applications based on both fiber and free space data links, such as local triggering and data readout and trigger-clock distribution, are also discussed.