verifies that the fault condition is still present referring to fig9 after the substitute reflective state has been enabled and incoming traffic a on the first input waveguide 16 is redirected to the second output waveguide 22 a u2192 d the second reverse traffic detector 40 monitors for traffic c received over the second input waveguide 20 because the switch is in the reflective state any such traffic will be reflected onto the second intermediate waveguide 26 where it is detected by the second reverse traffic detector 40 if incoming traffic c is detected it is presumed that the fault condition for the input for the second path 14 has been repaired it is further assumed that the fault condition for the output b along the first path 12 has also been repaired consequently the switch controller 46 enables the normal transmissive state and the optical switch 10 resumes operation over paths a u2192 b and c u2192 d as shown in fig7 in the operation of the optical switch of the present invention it is assumed that if incoming traffic is not detected on one of the input waveguides for example signals c of the second input waveguide 20 then the other path namely the path 12 is also damaged downstream of the switch although this assumption can prevent transmission of data down the malfunctioning destination line it is possible that the malfunction.