OSNR Monitoring Method for OOK and DPSK Based on Optical Delay Interferometer

A Fully-integrated In-band OSNR Monitor using a Wavelength-tunable Silicon Microring Resonator and Photodiode

“…Based on silicon photonic components, the demonstrated OSNR monitor has the potential to be low cost and be directly integrated with auxiliary microelectronics. In addition, with the maturing of silicon photonics technology [16], OSNR monitors based on other principles such as the 1-bit [4] or ¼-bit [5] delay line interferometers, can also be fabricated in one single chip, enabling powerful OPM components for future impairment-aware optical networks. …”

“…However, this technique may not be accurate when the noise is partially polarized or in the presence of polarization-mode dispersion (PMD), and it is difficult to realize in integrated optics. Another method, based on mach-zehnder interferometry [4][5][6], requires the prior knowledge of the signal amplitude autocorrelation function and therefore typically requires system calibration by turning off the noise and scanning signal interference [6]. Recently several efforts [7][8][9] have been made to realize OSNR monitoring in an integrated fashion, however these demonstrations still require discrete and bulky off-chip components such as power meters.…”

Dual Polarization Interferometric In-Band OSNR Measurement

“…A number of techniques exist for this purpose; these include the polarization nulling method [3] and orthogonal polarization heterodyne mixing [4]. It is also possible to use an interferometer to exploit the coherence difference between signal and ASE in order to calculate the OSNR [5][6][7], but this carries with it the requirement for prior knowledge of the signal coherence properties. This problem may be solved through use of a pair of Michelson fibre interferometers with different optical delays of duration much shorter than the bit period of the signal [8].…”

Interferometer based in-band OSNR monitoring of single and dual polarisation QPSK signals

“…However, this relies on the assumption that the noise is fully unpolarised 4 . A mach-zehnder interferometer has been shown to address the issues of polarised noise, chromatic dispersion and PMD [5][6][7] . However such a device relies on prior knowledge of the coherence of the signal, must be calibrated for each modulator.…”