A few years back we had a Acterna Testpad FST2802 (datasheet) on loan from a vendor to test a big rollout of fiber we did together. As we only had one unit we couldn't use it to test other things then the rollout where the vendor had the other unit. So I decided to write a little software program to act as a software based reflector.
$ ./acternabnc Acterna TestPad FST-2802 Linux Loopback (c) 2011 Unilogic Networks B.V. Release: August 12th 2011 Usage: acternabnc <ip remote unit>
Configure the Acterna with a fixed IP and configure the IP of the software client on it. It will only do L3 tests, no L2 or BER.