High-sensitivity external modulator data link for high-energy particle detector diagnostics

Kent G. McCammon, Mark E. Lowry, Yuan Hann Chang, Paul Parker, Bolek Wyslouch, Craig Wuest, Charles F. McConaghy, Ulrich Becker

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


An analog fiber-optic data link has been demonstrated for direct charge readout of wire chambers used in high energy particle detectors. The fiber link consists of a Nd:YAG laser carrier, a Mach-Zehnder external modulator, and a low-noise optical receiver. A charge pulse developed on a sensing wire flows directly into the electro-optic modulator with no preamplification. The substitution of passive modulators and fiber cable for active electronics and copper wire near large collider detectors has clear advantages with regard to radiation damage susceptibility, EMI immunity, physical size, and power consumption. Also, the modulator performance was unaffected for an applied one Tesla magnetic field. Reduction of noise contributions from the laser carrier and optical receiver and exploitation of the 'effective optical gain' properties of external modulators resulted in shot-noise-limited link sensitivity. Modulators were packaged with large termination resistors enabling increased charge sensitivity with an increased system risetime tradeoff. Energy resolution of the fiber link was comparable to preamps conditional on large terminations and subsequent slow readout. For shorter risetimes required in timing diagnostics, small termination resulted in sensitivity 6.8 times inferior to preamps. Several potential improvements in sensitivity are discussed.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherPubl by Int Soc for Optical Engineering
Number of pages10
ISBN (Print)0819409693, 9780819409690
StatePublished - 1993
EventAnalog Photonics - Boston, MA, USA
Duration: 10 Sep 199211 Sep 1992

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceAnalog Photonics
CityBoston, MA, USA


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