The OC3 line should be 155.52 MBps both ways, (upload and download), but that does not equal out to 2*155. you are only getting 155 MBps, it is just a synchronous connection, (meaning speed is same both ways unlike DSL which is asynchronous, much faster download than upload) minus your overhead.
“An OC3 can be three DS3s (T3s) or one 155M pipe. The benefit in using DS3s is that each can be separated back out as individual T1s (each with 24 channels). To put it into perspective, the speed of an OC3 connection is 155Mbps. This is equivalent to 3 T3 lines or 100 T1 lines. An OC12 connection is 622Mbps, equivalent to 14 T3 lines or approx. 414 T1 lines.”