Modulation-format-independent OSNR monitoring insensitive to cascaded filtering effects by low-cost coherent receptions and RF power measurements

Abstract

Optical signal-to-noise ratio (OSNR) monitoring is indispensable for ensuring robust and flexible optical networks that provide failure diagnosis, dynamic lightpath provisioning and modulation format adaptation. We propose and experimentally demonstrate a low-cost, modulation-format-independent OSNR monitoring scheme utilizing reduced-complexity coherent receptions, electrical filtering and radio frequency (RF) power measurements. By measuring the RF power of the coherently received baseband signals at three different frequency components, the proposed OSNR monitor is also insensitive to spectral narrowing induced by cascaded wavelength selective switches (WSSs). We experimentally demonstrate accurate data-format-transparent and filtering-effect-insensitive OSNR monitoring for 25-Gbaud dual-polarization (DP-) transmissions with QPSK, 16-QAM and 64-QAM signals over various distances with different amount of filtering effects by cascaded WSSs. We further characterize the influence of different system parameters, such as the bandwidth of the electrical low-pass filter, the laser frequency offset and laser linewidth on the accuracy of the proposed OSNR monitor. The robustness of the proposed OSNR monitoring scheme to fiber nonlinearities, calibration parameter mismatches and variations of WSS parameters are also investigated.

Self-Learning Monitoring On-Demand Strategy for Optical Networks

“…This method has been proven to be MF independent and WSS filtering effect insensitive. In real applications this monitoring function can be implemented using lower cost coherent reception and an RF measurement device [22], [23]. To realize physical layer autonomous in-band OSNR monitoring, single channel filtering is important so that the algorithm can autonomously locate the central frequency by searching for the maximum power (as there is only one channel).…”

“…Two parameters α and β are introduced to model WSS filtering penalty on the signal spectrum. By monitoring the spectral powers P CF1 , P OF2 , P OF3 after transmission, we have [22] P CF1 = P s1 + P n1 (1)…”

Blind modulation format identification for digital coherent receivers

“…Several techniques are available in the literature for blind OSNR monitoring [11][12][13][14]. We have adopted a recently proposed in-band OSNR monitoring scheme [13] for our MFI technique.…”

“…Several techniques are available in the literature for blind OSNR monitoring [11][12][13][14]. We have adopted a recently proposed in-band OSNR monitoring scheme [13] for our MFI technique. Figure 1(a) shows the schematic diagram of the proposed in-band OSNR monitor deployed at the intermediate network nodes which consists of a tunable laser, a 3 dB coupler, a low speed balance detector, a low pass electrical filter, an electric power meter and a control and process unit (CPU).…”

“…1(b)-(c)). The relationship among P CF , P OF , signal power (P SIG ) and amplified spontaneous emission (ASE) noise power (P ASE ) can be described as [13]:…”