Over the next week, Caltrain will be laying down fiberoptic cable along its tracks as part of its modernization efforts. Sunnyvale residents near the tracks may experience some late-night disturbances. The specific times are Saturday November 2nd from 8 p.m. to 6 a.m. and Tuesday November 5th through Thursday November 7th from 8 p.m. to 4 a.m. You can read the full press release here. The work primarily involves trenching and boring efforts, depending on the location.
This is part of an effort to implement the Communications Based Overlay Signal System (CBOSS) Positive Train Control (PTC) Project. This is a train safety system that will become more necessary if Caltrain is to share tracks with both freight traffic (already using the tracks) and high-speed rail. The plan is to install a fiberoptic network alongside the track which has sufficient bandwidth to not only handle CBOSS PTC network traffic, but also provide additional capacity for future Caltrain needs and possibly even capacity for commercial resale, as a revenue source for Caltrain.