| 142 |
|
There is one AOH |
| 143 |
|
per module, sitting on a ledge glued on the cooling pipe very close to |
| 144 |
|
the front-end hybrid. Multi-mode optical fibers~\cite{ref:opto} |
| 145 |
< |
transport the signal to the counting room where the FEDs~\cite{ref:fed} |
| 145 |
> |
transport the signal to the counting room where the |
| 146 |
> |
Front End Drivers (FEDs)~\cite{ref:fed} |
| 147 |
|
convert back the signal to an electrical one and digitize it. |
| 148 |
|
Each AOH has two or three two meter long pig-tail |
| 149 |
|
optical fibres ending with an optical plug.\\ |
| 165 |
|
\label{fig:ctrlring} |
| 166 |
|
|
| 167 |
|
The control of the modules front-end electronic is implemented by means of a |
| 168 |
< |
hierarchical structure organized in groups of modules~\cite{ref:dohm}. Each group is |
| 169 |
< |
controlled by a Communication and Control Unit (CCU) taht represents a |
| 168 |
> |
hierarchical structure organized in groups of modules~\cite{ref:dohm}. |
| 169 |
> |
Each group is |
| 170 |
> |
controlled by a Communication and Control Unit (CCU)~\cite{ref:ccu} |
| 171 |
> |
that represents a |
| 172 |
|
``node'' in a ``token-ring'' formed by several daisy-chained CCUs and |
| 173 |
|
known as {\it control ring}. The control ring is mastered by a Front End |
| 174 |
|
Controller, FEC~\cite{ref:opto}, located outside the experiment by |
| 176 |
|
Control Rings. |
| 177 |
|
|
| 178 |
|
\begin{description} |
| 179 |
< |
\item[Digital Opto Hybrid Module] The FEC optical signals are converted into electrical signals by two DOHs |
| 180 |
< |
(Digital Opto-Hybrid) that send clock, trigger, and control signals to |
| 179 |
> |
\item[Digital Opto Hybrid Module] The FEC optical signals are converted into electrical signals |
| 180 |
> |
by two |
| 181 |
> |
Digital Opto-Hybrids (DOHs)~\cite{ref:doh} that send clock, trigger, and control signals to |
| 182 |
|
the token ring of CCUs. The DOHs are physically located on a board, |
| 183 |
< |
Digital Opto Hybrid Module~\cite{ref:dohm} (DOHM), that provides up to |
| 183 |
> |
Digital Opto Hybrid Module (DOHM)~\cite{ref:dohm}, that provides up to |
| 184 |
|
15 ports (7 on the main DOHM board plus 8 on its |
| 185 |
|
secondary extension or AUX) to implement the token ring. Each port |
| 186 |
|
connects the DOHM to a CCU located on the Mother Cable head |
