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Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies within which a fiber optic component, link or network will operate.
Extinction Ratio (ER)
Extinction Ratio is the ratio of two optical power levels, of a digital signal generated by an optical source, (example a laser diode), where P1 is the optical power level generated when the light source is "on," and P0 is the power level generated when the light source is "off." The extinction ratio may be expressed as a fraction, in dB, or as a percentage.
Optical Signal-to-noise Ratio (OSNR)
Optical Signal-to-noise ratio is the ratio between the signal power and the noise power in a given bandwidth. Most commonly a reference bandwidth of 0.1 nm is used. This bandwidth is independent from the modulation format, the frequency and the receiver. For instance a OSNR of 20dB/0.1nm could be given, even the signal of 40 GBit DPSK would not fit in this bandwidth. OSNR is measured with a Optical Spectrum Analyzer. It is generally measured at the wavelength of interest.
Repeatability is the variation in a number of repeated measured quantities when measurement conditions are changed and restored. The value corresponds to half the spread between the minimum and maximum value measured.
Wavelength Repeatability is the random uncertainty in reproducing a wavelength after detuning and re-setting the wavelength. The wavelength repeatability is ± half the span between the maximum and the minimum value of all actual values of these wavelengths. Example test condition: uninterrupted TLS output power, constant power level, temperature within operating temperature range, coherence control off, short time span. Note: NOTE The long-term wavelength repeatability can be obtained by taken the wavelength repeatability and wavelength stability into account.