We present a theoretical and experimental evaluation of the tolerance between optical labels and payloads in an optical router with 10-Gb/s packet payload and 155-Mb/s subcarrier multiplexing encoded label. The label processing functions are described in detail and alignment aspects are precisely evaluated by changing separately the arrival time of both label and payload signals. For the first time to our knowledge the experimental verification allows us to evaluate the delay tolerance in the process of coding the baseband label onto the optical packet without affecting the normal operation of the router. According to the router parameters, the maximum range of misalignment is estimated to be around 100-120 ns.