Abstract: Embodiments of the present invention relate to method and device for measuring optical signal-to-noise ratio (OSNR). A method for measuring an OSNR of a signal of interest may comprise: obtaining spectrum of the signal of interest, the spectrum including power spectrum density distribution of the signal of interest in a channel bandwidth B; obtaining spectrum of a comparative signal that has the same spectrum characteristics as but different OSNR than the signal of interest, the spectrum including power spectrum density distribution of the comparative signal in the channel bandwidth B; and calculating the OSNR of the signal of interest by using the spectrum of the signal of interest and the spectrum of a comparative signal.

Abstract: Embodiments of the present invention relate to method and device for measuring optical signal-to-noise ratio (OSNR). A method for measuring an OSNR of a signal of interest may comprise: obtaining spectrum of the signal of interest, the spectrum including power spectrum density distribution of the signal of interest in a channel bandwidth B; obtaining spectrum of a comparative signal that has the same spectrum characteristics as but different OSNR than the signal of interest, the spectrum including power spectrum density distribution of the comparative signal in the channel bandwidth B; and calculating the OSNR of the signal of interest by using the spectrum of the signal of interest and the spectrum of a comparative signal.

Abstract: An OSNR measuring method, comprising: measuring a spectrum to be measured of an optical signal at a point to be measured of an optical transmission line, and acquiring the comparative spectrum of the optical signal within a channel wavelength range and at an SNR different from the SNR of the point to be measured; respectively integrating, within the channel wavelength range of the optical signal, the spectrum to be measured and the comparative spectrum to obtain total power Pspectrum to be measured and Pcomparative spectrum, and acquiring a noise factor F and a signal scale factor A; calculating, according to the total power, the noise factor and the signal scale factor, the noise power Pspectrum to be measured within the channel wavelength range of the optical signal, so as to obtain an OSNR of the point to be measured.

Abstract: A single longitudinal-mode laser includes a first mirror and a second mirror that define a laser cavity therein that does not include a linear polarizer. A birefringent gain medium can generate a lasing light at a lasing wavelength along a light propagation direction in response to a pump light at a pumping wavelength. The birefringent gain medium has an optical axis substantially perpendicular to the light propagation direction. A first wave plate positioned between the first mirror and the birefringent gain medium is a quarter wave plate at the lasing wavelength and a whole wave plate at the pumping wavelength. A second wave plate is positioned between the birefringent gain medium and the second mirror. The first wave plat and the second wave plate in part produce a single longitudinal mode in the lasing light.

Abstract: A single longitudinal-mode laser includes a first mirror and a second mirror that define a laser cavity therein that does not include a linear polarizer. A birefringent gain medium can generate a lasing light at a lasing wavelength along a light propagation direction in response to a pump light at a pumping wavelength. The birefringent gain medium has an optical axis substantially perpendicular to the light propagation direction. A first wave plate positioned between the first mirror and the birefringent gain medium is a quarter wave plate at the lasing wavelength and a whole wave plate at the pumping wavelength. A second wave plate is positioned between the birefringent gain medium and the second mirror. The first wave plat and the second wave plate in part produce a single longitudinal mode in the lasing light.