pdl lt 0 05 db for the high speed gt 10 gb s optical network such as 40 gb s transfer rate fig9 demonstrates another embodiment where the first reflection device 108 and the second reflection device 112 of fig1 are replaced by first and second beam splitters 608 and 612 the first beam splitter 608 reflects most of light but taps out a small percentage i e 1 5 of the light intensity such a tap out light beam is detected by a photo diode detector 602 which just sits behind the splitter 608 similarly the second beam splitter 612 also reflects mot of light and also taps out a similar small percentage i e 1 5 of the incoming light a second photo diode detector 604 is placed behind the second beam splitter 612 and detects the tap out signal from the second beam splitter 612 the tap out signals from the first photo detector 602 and the second photo detector 604 gives the actuarial values of the incoming and outgoing light power respectively it means that this voa device provides option of real time monitoring light power in the optical network thus resulting in great advantage for the optical network.