Operational communcation network
 

Hello, I am looking for "Operational Communication Network" definition. Where can I find this definition. Thanks in advanced

Never heard of it. We operate Aeronautical Fixed Telecommunications Network (AFTN) and Aeronautical Mobile Telecommunications Network. The latter is operational communications between the ground and aircraft, the former is communications using teleprinters or computers for admin or operational use eg passing of flight plans and NOTAMs etc

tow-bar, there is the ATOTN? Air Traffic Operational Telephone Network.

Operational Communications known as OPC are VHF frequencies which are dedicated for very specific uses and for which an ATCO or FISO licence or an Air/Ground Certificate of Competence is not required.
Airline company frequencies come under this as well companies operating on behalf of the MOD.

Have a look at the following.

CAP 413, Radiotelephony Manual, Chapter 9, Page 3, 1.6 Aircraft Operating Agency Messages

As telstarr says, the most common use of OPC that you'll probably come across is company/handling agent frequencies.