Tata Sudhakar

Bio: Tata Sudhakar is an academic researcher from National Institute of Ocean Technology. The author has contributed to research in topics: Drifter & Ocean observations. The author has an hindex of 6, co-authored 33 publications receiving 110 citations.

Fiber optic sensors in ocean observation: A comprehensive review

Abstract: A survey of recent investigations on ocean sensors is carried out with a specific focus on fiber optic sensing methods, materials for fabricating sensor head and sensor performance. Four categories of fiber optic sensing structures, including interferometer, fiber grating, photonic crystal fiber, and surface plasmon resonance are reviewed. These techniques measure physical and chemical variations of sensitive optical fibers and reveal changes in properties of the optical signal when exposed to the ocean environment. Advantages and disadvantages of all the sensing schemes are discussed and compared. Hybrid sensors that combine different optical sensing techniques are also discussed.

Development of a highly accurate and fast responsive salinity sensor based on Nuttall apodized Fiber Bragg Grating coated with hygroscopic polymer for ocean observation

Abstract: This paper experimentally demonstrates the salinity sensing characteristic of an apodized Fiber Bragg Grating (FBG) coated with a hygroscopic polymer. Polyimide (PI) was used as the coating material on the FBG inscribed with Nuttall apodization function. PI coating enhances sensitivity by its hygroscopic property and apodization increases detection accuracy by reducing side lobes in the reflected spectrum. Based on experimental results, it was observed that the proposed salinity sensor has a sensitivity of 0.0026 nm/Practical Salinity Unit (PSU) with a resolution of 0.115 PSU in the range of 0 PSU to 40 PSU with an average response time of 60 seconds. Validation results using commercially available ocean sensors indicated that the proposed optical fiber sensor is capable of measuring seawater salinity with a mean error of 0.2015 PSU.

Computational analysis of thermally induced stress in corrosion-resistant metal coated fiber optic sensors for oceanographic application

Abstract: Sensors deployed for ocean observation are highly corroded by seawater. This study deals with the analysis of corrosion-resistant metal coated Fiber Bragg Grating (FBG) sensors for ocean temperature sensing. Firstly, the effect of thermally induced strain on FBG sensors coated with corrosion-resistant metal/alloy was computationally analyzed using Hookes law that reveals thermal strain sensitivity ranging from 28.6 μϵ/°C to 38.3 μϵ/°C for Stainless Steel 316L, Nickel and Nickel–Chromium alloy. This was followed by determining temperature sensing coefficient of FBG sensors coated with above mentioned metals/alloys that showed sensitivity ranging from 56.3 pm/°C to 75.3 pm/°C for two types of photosensitive fibers such as Germanium doped and Boron co-doped silica fibers for ocean temperature varying from 20 °C to 30 °C.

A Capacitive-Coupled Noncontact Probe for the Measurement of Conductivity of Liquids

Abstract: A noncontact (capacitive-coupled) probe for the measurement of the conductivity of liquids is presented. Insulation introduced between the measurement electrodes and the liquid intrudes a couple of coupling capacitances. Though the capacitive coupling overcomes the problems of electrode polarization and contamination associated with contacting electrodes, the large reactances of the coupling capacitors pose a problem in the measurement of comparatively very small resistance of the liquid. An auto-balancing signal conditioning scheme presented here overcomes the problem posed by the large capacitive reactances and provides directly a measurable output proportional only to the conductance of the liquid. Error analysis of the probe presented herein helps the optimal design of the probe. A worst case error of ± 0.9% was obtained from a prototype noncontact conductivity probe, developed and tested.

Development and experimental validation of a Nuttall apodized fiber Bragg Grating sensor with a hydrophobic polymer coating suitable for monitoring sea surface temperature

Abstract: Continuous monitoring of Sea Surface Temperature (SST) is essential for predicting and understanding various complex meteorological processes. In this work, a novel fiber optic temperature sensor based on an apodized Fiber Bragg Grating (FBG) is proposed for measuring variations in SST. The sensor head is fabricated based on optimized grating profile and coating material. Experimental analysis reveals that the proposed sensor yields a temperature sensitivity of 13 pm/ ° C with a resolution of 0.023 ° C in the temperature ranging from 16 ° C to 30 ° C . Performance of the proposed temperature sensor is validated against commercial ocean sensors which provides a mean error of 0.2342 ° C thereby proving the potential of the proposed FBG sensor for efficient SST monitoring in real-time.

A Wireless Sensor Network.

Abstract: The Wireless sensor network play a vital role in collecting a Real – Time data, monitoring environmental conditions based on technology adoption. These sensor network is the combination of sensing, computation, and communication through a single tiny device. Here many tiny nodes assemble and configure themselves. It also controls actuators that extend control from cyberspace into the physical world. Here the sensor nodes communicate with the local peers rather than the high – power control tower or base station. Instead, of relying on a predeployed infrastructure, each individual sensor or actuator become part of the overall infrastructure. Here we have three hardware platforms that addresses the needs of wireless sensor netwoks. The operating system here uses an event based execution to support concurrency. The platform serves as a baseline and does not contain any hardware accelerators. . First platform serves as a baseline and it produces Operating system concepts for refining concurrency mechanisms. The second node validates the architectural designs and improve the communicational rates. The third node represents the full realization of the general architecture. Keywords— node, platform, concurrency.

Optical fiber sensing for marine environment and marine structural health monitoring: A review

Abstract: Optical fiber sensors have attracted considerable attention for marine environment and marine structural health monitoring, owing to advantages including resistance to electromagnetic interference, durability under extreme temperature and pressures, light weight, high transmission rate, small size and flexibility. In this paper, the optical fiber sensors employed for marine environment and marine structural health monitoring are summarized for the understanding of their basic sensing principles, and their various sensing applications such as physical parameters, chemical parameters and structural health monitoring. This review paper shows the feasibility of using optical fiber sensing technology for marine application and, due to the aforementioned advantages, it is possible to envisage a widespread use in this research field in the next few years.

Fiber-Optic Chemical Sensors and Biosensors (2015-2019).

Abstract: High-quality optical fibers can be produced now at a low cost and large quantity, and this has further promoted the development of fiber optic (chemical) sensors. After over 30 years of innovation, fiber optic sensing technology has become mature because of acceptable costs, compact instrumentation, high accuracy and the capability of performing measurements at inaccessible sites, over large distances, in strong (electro)magnetic fields and in harsh environment. The technology is still proceeding quickly in terms of innovation, and respective applications have been found in highly diversified fields. This review covers work published in the time period between October 2015 and October 2019. It is written in continuation of previous reviews.

Recent progress in and perspectives of underwater wireless optical communication

Abstract: Underwater wireless optical communication (UWOC) is an emerging and feasible underwater communication technology and has developed rapidly in recent years. Building a high-performance and practical UWOC system requires comprehensive consideration and optimization design from the device to the system, as well as from the internal modulation to the external environment. This paper provides an overview of the recent developments in UWOC systems, covering aspects about the system transmitters and receivers, advanced modulation formats and underwater channels. Some key technologies to improve transmission capacity of UWOC are classified and summarized to provide guidance for system design. The main challenges and perspectives to achieve a reliable UWOC system are also mentioned. The summary and analysis of these advances and techniques will shed light on the future development of UWOC technology and assist in the construction of the internet of underwater things.

OMNI buoy network in the Bay of Bengal

Abstract: The Bay of Bengal, the northeastern limb of the tropical Indian Ocean is a region strongly coupled with summer and winter monsoons and tropical cyclones. The Bay is also a region of strong vertical stratification near the surface due to large inputs of freshwater through rainfall and river run-off. In situ subsurface ocean measurements are quite sparse both in space and time in this region. The National Institute of Ocean Technology (NIOT), Chennai deployed instrumented moored buoys in the Bay since 1997 to provide continuous time-series measurements of surface meteorological and oceanographic parameters at selected locations. In the recent years several studies have shown the important role of variability of heat storage in the near-surface layers on the intraseasonal and interannual evolution of monsoons and cyclones. Hence a strong need was felt to augment some of these buoys with subsurface temperature, salinity and current sensors to continuously record the temporal evolution of their vertical structures. Under a new initiative, NIOT has deployed six moored buoys attached with sensors to collect subsurface oceanographic parameters on real-time basis in the Bay. These are coded as the OMNI (Ocean Moored buoy Network for Northern Indian Ocean) buoy system. The time-series of vertical profiles of temperature and salinity in 500 m water column from the surface and currents in the topmost 100 m water column are monitored at discrete depths in the Bay. The OMNI buoy programme addresses a long-standing need to understand the observed variability of upper ocean thermohaline and current structures on several timescales that has important bearing on the evolution of seasonal monsoons and cyclones. This article presents an account on the evolution, status and usefulness of the OMNI buoy programme.