We experimentally realize seamless operations with below 100-fs timing jitter in a 10-GSample/s 3-bit photonic analog-to-digital converter (ADC) with an input 2.5-GHz sinusoidal electrical signal. To address the energy efficiency, it is necessary to explore some serial approaches to get most operations in a photonic ADC done before serial-to-parallel conversion to save the number of devices. To press forward with the work on subsequent operations after optical sampling in a photonic ADC, we have investigated optical quantization and coding and demonstrated their performances. The experimental results successfully demonstrated seamless operations in a photonic ADC, i.e., sampling, quantization, and coding, while keeping its parallel-configuration-free characteristics and low timing jitter below 100 fs. This demonstration could address the energy efficiency by reduction of the number of devices, including electrical ADCs for subsequent operations after optical sampling in existing high-performance photonic ADCs.

This paper presents a pH sensor with a Mach–Zehnder Interferometer (MZI) that operates in solutions of 4.0, 7.0, and 10.0. The sensor device consists of two tapered sections with dimensions of 1 mm/1 mm/1 mm for down-taper, waist-length, and up-taper, respectively, with a separation of 10 mm. The diameter of the waist is 40 $\mathsf{\mu }$m. This work includes the experimental evaluation of an MZI fiber optic pH sensor at 1559 nm, where 1559 nm represents a specific wavelength chosen for its optimal sensitivity in evaluating the sensor pH detection performance. It is not the central wavelength of the optical fiber, but one of the minimal values selected to enhance the interaction between the evanescent field and the sample, ensuring the reliable detection of pH variations. These sensor dimensions and the functionalized solution of multi-walled carbon nanotubes (MWCNTs) increase the detection of pH in dyes used in the textile industry. Alizarin is a strong anionic red dye that is part of the anthraquinone dye group. The experimental results demonstrated effective detection of pH levels in water contamination involving dye. This development could resolve the problem with Alizarin. The simple fabrication, low cost, and stability of the optical response make this sensor relevant for pH measurements in water contamination.

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