We present the performance analysis of 112 Gb/s×4 wavelength division multiplexing (WDM) 100 GHz channel spacing polarization division multiplexed-differential quadrature phase shift keying (PDM-DQPSK) optical label switching system with frequency swept coherent detected spectral amplitude code labels. Direct detection is chosen to demodulate the payload by applying a polarization tracker, while 4-bits of 156 Mb/s spectral amplitude code label is coherently detected with a scheme of frequently-swept coherent detection. We optimize the payload laser linewidth as well as the frequency spacing between the payload and label. The label and payload signal performances are assessed by the eye-diagram opening factor (EOF) and bit-error rate (BER) at 10-9 as a function of the received optical power (ROP) and the optical signal to noise ratio (OSNR). The payload could well be demodulated after 900 km at a bit error rate of 10×3 using forward error correction (FEC).