TTC Laser Transmitters TTCex, TTCtx

The TTCex and TTCtx Laser Transmitters were designed for the optical transmission of Timing, Trigger and Control (TTC) signals to many thousands of destinations in the front-end electronics of high-energy particle physics experiments at CERN's Large Hadron Collider (LHC). Both transmitters are single-width 6U VMEbus size and use only standard VME +5 V, +12 V and -12 V power supplies, a -5.2 V ECL supply being derived from an on-board regulator. The transmitters can be used separately or in combination to match the requirements of a variety of different TTC distribution architectures. Both use a custom version of the Photon PT5343-13-3-ST laser transmitter with special accurately-matched short 30 cm singlemode optical fibre pigtails. The 1310 nm wavelength was chosen because low chromatic dispersion is more important than low fibre attenuation in this application. Each VME crate full of these modules can broadcast to a total of 8960 destinations, divided into between 1 and 40 trigger partitions.

TTCex
The TTCex transmitter provides 10 optical outputs, each of which can be fanned out by a 1:32 optical tree coupler to broadcast to a total of 320 destinations. The transmitter contains two biphase mark encoders driven by a common internal 160.316 MHz VCXO/PLL with very low jitter. It can be operated as a single unit, or in independent halves to feed two small partitions of up to 160 destinations each. Outputs from the encoders are provided to drive extension TTCtx transmitters to broadcast to larger partitions. Each encoder has an input for a low-latency A channel for the Level-1 trigger accept and a B channel for broadcast and individually-addressed commands and data. The clock input of each TTCex is driven by the 40.079 MHz bunch-crossing clock of the LHC. The power consumption of the module is about 16W.

TTCtx
The TTCtx transmitter is similar to the TTCex but has 14 optical outputs instead of 10 and does not contain any encoders. It can be operated in independent halves to feed two small partitions of up to 224 destinations each, or as a single unit to feed a total of 448 destinations. An electrical output is provided to allow several TTCtx modules to be daisy-chained to broadcast to larger partitions. Since TTCtx modules do not contain encoders they must be driven by a TTCex module. The power consumption of the module is about 10W.

When the TTCtx is configured in Single mode the I/P socket is associated with all the optical outputs 1 to 14. When the transmitter is in Dual mode it is associated with the lower group of outputs 8 to 14. The I/O socket on the TTCtx front panel is an input or an output according to the configuration of the module. When the module is in Single mode, the socket provides a buffered output of the input signal for daisy-chaining to additional TTCtx transmitters. When the module is in Dual mode, it becomes an input socket for the signal associated with the upper group of optical outputs 1 to 7. All electrical inputs and outputs use Lemo coax connectors and are ECL-swing 50Ω AC-coupled except for the two data channel inputs to the TTCex, which are DC-coupled.

Although the hazard level of the TTCex and TTCtx lasers is Class 1, output connectors or fibre ends should not be viewed with optical instruments. The transmitters are equipped with a front panel switch that allows all the optical outputs to be disabled, and the lasers can also be disabled via the VMEbus.

The TTCex and TTCtx transmitters were designed by Bruce Taylor. Following competitive tendering, production was carried out by various manufacturers.

In questo link sono elencati 28 modelli, di cui 28 con immagini e 3 con schemi.
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