Mach-Zehnder Interferometer Demodulation Research Articles

Research of Fiber Bragg Grating Sensor Demodulating Technology with Lab VIEW

Combining the virtual instrument technology with the fiber Bragg grating sensing technology, a new fiber Bragg grating sensing demodulation system based on Lab VIEW has been designed. The unbalanced Mach-Zehnder interferometer demodulation technology has been used in this system to translate the fiber Bragg grating wavelength signals in which the strain information is contained into the phase signals，and transfer it to the virtual instrument based on Lab VIEW with the high speed data acquisition card，then conduct process operations and results display [1]. At last, the value of measured strain can be obtained. Compared with the conventional demodulations system，the accuracy this interferometer demodulation system’s measurement has been increased greatly. At the same time, it solves the problem of high cost, large volume and only displays the wavelength with the conventional demodulations system.

Impact of random angular jitter on fiber-coupled differential phase-shift keying receivers with Mach–Zehnder interferometer demodulation

In an optically preamplified differential phase-shift keying (DPSK) receiver with Mach–Zehnder interferometer (MZI) demodulation, it is essential to couple free space light into a single-mode fiber, by which the received optical signal can be guided into the amplifier and MZI. Random angular jitter has a profound impact on fiber coupling efficiency, in that it would significantly deteriorate the receiver performance. In this paper, the average bit error rate (BER) of fiber-coupled DPSK receivers is obtained in the presence of random angular jitter. It is shown that the degradation is significant when the random angular jitter normalized by the mode field radius is larger than 0.3. We further analyze the impact of other factors, including central obstruction and optical filter transfer functions. Our results show that the super-Gaussian filter outperforms other filters and leads to lower average BER at a fixed optical signal-to-noise ratio. This work can be used to improve the design of fiber-coupled DPSK receivers.

Probability density function of noise statistics for optically pre-amplified DPSK receivers with optical Mach–Zehnder interferometer demodulation

We present explicitly semi-analytical probability density functions (pdf’s) of noise statistics in DPSK receivers with Mach–Zehnder interferometer (MZI) demodulation with considering the phase noise for the first time. Error performance of DPSK receivers with MZI demodulation is evaluated by using the calculated pdf’s. It is found that DPSK receivers with MZI demodulation and balanced detection are less sensitive to phase noise impact than those with the single-port detection to some extent. Moreover, it is found that ASE–ASE beat noise induced pdf difference in balanced detection compared to single-port detection may result in ∼3dB improvement in receiver sensitivity mainly depending on optical filtering, ASE-amplified spontaneous emission. Therefore, the measured receiver sensitivity improvement by using balanced detection consist of the improvements due to signal energy difference and ASE–ASE beat noise induced pdf difference compared to single-port detection.

Noise statistics in optically preamplified differential phase-shift keying receivers with Mach–Zehnder interferometer demodulation: erratum

Noise statistics in optically preamplified differential phase-shift keying receivers with Mach–Zehnder interferometer demodulation: erratum

Noise statistics in optically preamplified differential phase-shift keying receivers with Mach-Zehnder interferometer demodulation.

We report an analysis of the noise statistics for an optically preamplified differential phase-shift keying (DPSK) receiver with balanced and single-port detections. It is found that identical signal-amplified spontaneous emission beating noise exists for bits 1 and 0 in DPSK balanced detection. It is also revealed that the bit error ratio (BER) of a DPSK receiver with balanced detection has no direct relation to the conventional Q factor. Moreover, an analytic BER expression for the DPSK balanced detection receiver is presented.

High-Resolution Interrogation Technique for Fiber Bragg crating Sensor Using Long-Period Fiber Grating Pair and Erbium-Doped fiber

A novel interrogation scheme to detect fine Bragg wavelength shift using a long period fiber grating pair with erbium-doped fiber inserted between the two gratings is reported. The technique is shown to feature high resolution and much more immunity to temperature perturbation compared to the conventioned Mach-Zehnder interferometer demodulation system. For quasi-static strain measurement, this approach provides high wavelength resolution of 0.05 pm that corresponds to 41.7 ne in strain and $3.8 $\times$ 10^{-3}$ $^{\circ}C$ in temperature. This interrogation system is also employed in dynamic measurement to obtain the minimum detectable strain perturbation of ~ 8.76 ne/H $z^{{\frac}{1}{2}}$ at 100 Hz. Moreover, this interrogation system has prominent thermal stability. This thermal stability comes from the fact that two arms of the interferometer, the core and cladding in erbium-doped fiber, are exposed to nearly the same environment .