A communication method includes combining first and second optical signals into a third optical signal, processing the third optical signal, and separating the third optical signal back into the first and second optical signals. The method includes sending the first optical signal out a first system port, sending the second optical signal out a second system port, receiving a fourth optical signal in the first system port, and receiving a fifth optical signal in the second system port. The method also includes combining the fourth and fifth optical signals into a sixth optical signal, processing the sixth optical signal, and separating the sixth optical signal back into the fourth and fifth optical signals.