An apparatus for testing multiple Small Form-Factor Pluggable Plus (SFP+) ports comprising: a first testing module; a second testing module; and a communications link coupled with the first and the second testing modules; wherein each of the testing modules includes: a SFP+ interface connectable to a port under test (PUT), a signal processing circuit including: a signal compensator configured to perform signal compensation on a signal received from the other testing module, and a signal modifier configured to: modify the compensated signal according to a set of predetermined modification parameters, and transmit the modified signal to the PUT.