Why are there two amplifiers inside an OAU board?

HI dear
1- Noise figure :- this value is so important because it represents the noise added by the amplifier to the signal , In OAU it is much better than using 2 amplifier boards .
2- Simplicity and compact design :- usually the signal travels for long distance needs first PRE-Amplifier which has high sensitivity to receive low power , then you need DCM which causes loss in the power of the optical signal then it should be amplified again to suitable level for demux or re-transmit so it needs Booster-Amplifier , OAU made it in 1 unit .
3- less slots in the chassis :- if you use PRE-Amplifier as a single unit and Booster-Amplifier also as a single unit you often need more slots.
4- single board in repeater mode:- when the NE is repeater you can use 1 OAU in each direction with no need for any other amplifier .
good luck

Dear user!

The PA gain is fixed, and the BA gain is adjustable. At the same time, a DCM is connected between the TDC and RDC. When the receive sensitivity of the amplifiers is the same, a longer transmission distance can be achieved by connecting the DCM to the two amplifiers.

Thank you!