Microwave Photonics for Optical Sensors

Temperature sensing scheme based on fiber ring microwave photonic filter with erbium doped fiber amplification

“…The sensitivity is estimated to be −5.89, −11.74, and −17.7 kHz/ C, respectively, when measuring the peak frequency shift of the passbands at 0.8, 1.6, and 2.4 GHz, which agrees well with the theoretical calculation above. From the theoretical analysis above, one can see from Equations (6) and (7) that the sensitivity of the sensing system based on fiber ring MPF is mainly decided by the measurement frequency as well as the ratio between the length of sensing fiber and the total length of the fiber ring. This conclusion also applies to other fiber ring structure-based sensors, and basically, when the ratio between the length of sensing fiber and fiber ring is fixed, the sensitivity will be determined if the measurement frequency is selected.…”

“…n , from which one can see that by measuring passband at higher frequency, higher sensitivity can be achieved, and there is an approximately linear relationship between the frequency shift and temperature change. According to the Equations (4) and (7), supposing that n is 1.45, l is 200 m, L is 205 m, η and α is 9.2 × 10 -6 and 0.55 × 10 -6 , 21,22 the sensitivity of the sensing system is calculated to be −5.38, −10.76, and − 16.14 kHz/ C, respectively, when the passbands at 0.8, 1.6, and 2.4 GHz are employed for sensing, which shows that by measuring passband at higher frequency range, higher sensitivity can be obtained.…”

Integrated Microwave Photonics for Wideband Signal Processing

“…In contrast, sensors based on microwave photonic signal processing techniques can conveniently convert the change in the optical domain to a corresponding variation in the microwave domain. The ability to perform measurements in the RF domain, which provides higher frequency resolution, enables a superior method for high resolution monitoring of miniscule changes in the measurand, thus enabling high performance sensing [74]. A much higher interrogation speed can also be obtained since the microwave frequency can readily be measured by a digital signal processor (DSP) with high speed and high resolution.…”

Integrated reconfigurable photonic filters based on interferometric fractional Hilbert transforms

“…6(d) are both feasible to implement the microwave photonic instantaneous frequency measurement (IFM). The essential concept is to investigate and establish the relationship between the unknown microwave signal frequency and the detected output power, which has been thoroughly demonstrated in the literature [15,20]. In the center of the output spectrum, the power is wavelength-dependent, as shown in Fig.…”