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Feasibility of Optical Wireless transmission systems for CTA
R. Corsini, A. Wajahat, E. CiaramellaScuola Superiore Sant’Anna, TeCP, Pisa, Italy
R. PaolettiUniversity of Siena and INFN Pisa, Italy
INFIERI Workshop, Madrid, Jan. 27th – 29th 2014
Outline
Motivation Optical wireless transmission system for CTA telescope Draft Requirements Open issues Draft activity list Conclusions and future perspective
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
SiPM camera for SST (Small Size Telescope)
Design of SST for CTA (Cherenkov Telescope Array)
• Single mirror
• Dual mirror
In dual mirror design the focal plane is
curved (spherical shape)
In camera design a specific solution
for curved-planar transition is needed
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
SiPM camera for Small Size TelescopeExample: CHEC (Compact High
Energy Camera ) camera for SST telescope
• Curved sensor plane
• Flat design for digitizer section and backplane
Transition
• Done with ribbon cables
• Near photo-sensors, decouples sensors+front end electronics from digitizers and backplane
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
SiPM camera for SST telescope
Curved focal plane
Readout modules based on analog digitizers
Transmit digital data to backplane electronics
Exploit wireless optical transmission to match modules to flat backplane
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
MotivationMain issues of the existing design
Transition between curved and flat surface done by
ribbon cable
Needs of reduction of electrical interconnections
Needs of stress-free module placement
Proposed solution• Optical wireless technology to connect sensors on
the curved surface with the flat layer of the backplane avoiding data transmission cables
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
Example of proposed solution
Alternative topology can be exploited
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
Optical Wireless Communications Characteristics
• No EMI with radio systems, no “e-smog”• Available and unregulated spectrum• Simple shielding by opaque surfaces → easily obtainable privacy• Flexibility of placement• Small form factor• Components (laser, PIN diode, electronics) available at low cost and
high reliability from telecom world
Motivation
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
DRAFT REQUIREMENTS:
• Bit rate = 100 Mbit/s, burst mode, 8B10B coded• L = 2 mm- 2 cm• Environmental requirements: outdoor• Power consumption?• Mechanical dimensions?• Mechanical and optical alignment tolerances?• Reliability requirements (life time, FIT, MTBF)?• Target Cost• ………..
Feasibility of Optical Wireless transmission systems at CTA
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
Open issue:
• Wavelength?• Source type?• Receiver Type and dimensions?• Package type?• Collimating Lens (material)?• Optical alignment and tolerances?• Power supply?
Feasibility of Optical Wireless transmission systems at CTA
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
Draft activity list
Specifications definition
Optical and Electrical/Electronic design
Components/sub systems specification definition
Components/sub systems selection and acquisition
Components/sub systems characterization
Prototype assembly and testing
……………
INFIERI Workshop, Madrid, Jan. 20th – 22th, 2014
Conclusions
Optical wireless is a viable solution for connection and transition between the curved surface topology of the sensors layer and the flat surface topology of the backplane layer.
No show stopper found at a first analysis
There are several challenges to integrate an optical wireless system on a Small Size Telescope for CTA in spite of its numerous advantages
