Laser Based Optical Links for the CMS Tracker: Options and Choices

The CMS tracker optical readout links must fulfill demanding requirements such as radiation hardness, high reliability, small size, low power dissipation and low cost while maintaining a high analogue transmission quality during the experiment lifetime. The concept adopted for the CMS tracker is based on edge emitting InGaAsP semiconductor lasers coupled to pure silica core single mode fibre at the front-end, and InGaAs pin photodiodes coupled to Ge-doped single mode fibre at the back-end. The wavelength of operation is 1.31µm. Three patch panels based on multiway single mode connectors are foreseen for ease of testing, installation and maintenance. Baseline choices such as transmitter type, fibre type, operation wavelength and modularity are explained and justified.