Design Of Radiation-Hard High-Speed Optical Transceiver ASICs In High-Energy Physics Detector Readout Systems

The Large Hadron Collider(LHC)is the world's largest and most powerful particle accelerator led by CERN(European Organization for Nuclear Research).There are four large-scale physics experiment detectors,ATLAS,CMS,LHCb,and ALICE on the four collision baselines of LHC.ATLAS and CMS detectors are famous for discovering the "God particle"Higgs boson in 2012.To support and expand the research scope of high-energy physics experiments,LHC will be upgraded in three stages.The upgraded LHC,called High-Luminosity LHC(HL-LHC),will operate at a mass-energy center of 14 TeV.HL-LHC poses higher radiation-tolerance requirements on the electronic devices for the detectors on HL-LHC,such as the general-purpose ATLAS detector.HL-LHC will increase the total number of collisions and provide massive amounts of data,requiring higher bandwidth of the optical fiber data link on the detector.The power supply system,cooling system and detectors are installed in a very tight space in high-energy physics experiments.The front-end optical fiber communication is limited by low temperature,high radiation,and power supply.The communication systems on the detector are not like commercial systems that can be replaced at any time.So,the optical fiber communication system in high-energy physics must have high reliability and low power,and the tolerance of low-temperature and high-radiation environments that is close to the interaction point of the detector.Recent studies have proved that the forward voltage of the VCSEL will increase resulting from the low-temperature and high-radiation environment.Under the high radiation dose requirements of the LHC,the forward voltage of the VCSEL increases more significantly,which will eventually cause the malfunction of the optical communication system on the detector.Therefore,research on high-speed optical transceiver chips in low-temperature and high-radiation environments,and small-size optical transceiver,is one of the key technologies in the upgrade of HL-LHC.We propose a charge pump adaptive to the cumulation of the radiation effects in a high-speed VCSEL array driver,which is the first time in high-energy physics experiments.The charge pump could raise the output voltage according to the radiation accumulation,which solve the problem of the malfunction of the VCSEL working in low-temperature and high-radiation environments.We design a four-channel high-speed VCSEL driver,namely cpVLAD.cpVLAD establishes a feedback mechanism between the driver and the charge pump,which realizes the output voltage of the charge pump auto-tracking the VCSEL forward voltage.The large noise of the charge pump is the main reason why the traditional high-speed VCSEL driver does not adopt a charge pump.The improved output stage uses a differential structure to suppress the charge pump noise effectively.cpVLAD uses an on-chip AC coupling circuit to eliminate the inconsistency of the common-mode voltage caused by multiple voltages of power supplies.Moreover,the AC coupling circuit can also adjust the cross point of the output signal to optimize the inherent time jitter of the output signal.cpVLAD can be operated at 10 Gbps under the temperature ranging from-35 ? to 65 ? and the total dose of 1 MGy.Since 2000,especially in the last 10 years,application-specific integrated circuits have been widely used in high-energy physics experiments.But the cost of integrated electrical packaging has always been a big problem.The number of chips used in the forefront of physics research is often only tens to tens of thousands.Compared with the millions of mass production in the industry or the support of almost unlimited resources in special fields,physicists must be self-reliant and find solutions to problems by themselves.At present,the optical transmitter chip and the receiver chip used in the high-energy physics experiment are independent.This thesis integrates the optical transmitter chip and the optical receiver chip with different functions for the first time,and realizes the two channels that can be configured as two transmitters or two receivers or one transmitter and one receiver.This attempt expands the scope of use and increases the production capacity,and provides a solution to the high cost of small batch optical transmitter chips in high-energy physics experiments,especially the packaging cost.This thesis mainly studies the following aspects.Firstly,the limiting amplifier with active feedback is used to solve the problem of imbalance between bandwidth and gain caused by process and radiation.Secondly,the configuration is realized by improving the driving ability of the output stage,which could configure the chip to drive the TOSA or PCB transmission line.Thirdly,I2C,DAC and other modules are designed in DLAS10 to realize the flexible programming configuration of the transmitting and receiving channels.In order to improve the ease of installation and reliability,we also designed a dual-channel optical module based on the LC optical interface.In an example of a high-energy physics experimental application(ATLAS LAr),its water-cooling system limits the height of the optical module to less than 6 mm.The height of the industry-standard SFP+optical module is 14mm.Based on the programmable radiation-hard transceiver chip DLAS10,combined with TOSA/ROSA,we customized the connector used to connect TOSA/ROSA and commercial LC interface,and realized the multi-functional optical module MTRx+,dual-channel transmitting optical module With MTx+ and dual-channel receiving MRx+,the overall height of the optical module is only 5.9 mm,and the optical module MTRx+is also in a leading position in terms of input sensitivity and power consumption.Based on the cpVLAD chip,the author also designed a small size optical module,QTRx,which is also suitable for the compact environment of the front-end readout system of high-energy physics experiments.The optical transceiver module QTRx is only 10 mm x 20 mm x 4 mm.It adopts an MT optical interface and provides 4 transmitter and 4 receiver channels.It is currently the highest channel density among the optical modules developed for high-energy physics experiment detectors.This research provides a solution to the space limitation of high-energy physics experiment detectors.At present,two chips and multiple optical modules have been designed and tested(except QTRx),and all specifications meet the requirements of optical fiber data links in high-energy physics experiments.They can be used in high-energy physics experiments in the future.