Fiber Optic Ship Hull Monitoring System

FBGs for ship hull monitoringThe ship’s hull, when floating or moving through the waters, is exposed to different types of forces. The magnitudes and points of those forces depend on the shape of the ship’s hull. The fiber optic ship hull monitoring system allows monitoring of not only the magnitude of strength but also its variation along the length of a continuous uninterrupted optical fiber. The distributed sensors also permit an easy and reliable comparison of a parameter at different points and the sensor cable measures at every point along the length with no “dead spots”. The ship’s integrity may be monitored in real-time by using optical fiber sensors. The collected data could be used to obtain a global condition of the ship’s hull. Ships monitoring can be relevant in the case of:

  • Strain-stress state monitoring of a ship hull
  • Cargo operations management on a tanker
  • Measurement of the draft and level in the ballast and service tanks
  • Fuel consumption monitoring system
  • Remote-controllable valves and gate valves
  • Main power auxiliaries monitoring (boilers, separators, etc.)
  • Vibration monitoring of the main ship aggregates
  • Fire detection
  • Warning solution on water entering into the cargo holds
  • Temperature measurement and control of the ship components

The mentioned system can also collect data from the hull monitoring system which can be used in the optimization of the ship’s design and operational availability. Continuous real data collection under different sea conditions and commercial operations enables the ship’s master/officers and other users interested in (ship’s owner, classification societies, ship’s insurance) to make correct conclusions about the actual ship’s hull state and about the necessary actions that have to be taken.

Optromix Company always takes part in the shipbuilding project. As an example, Optromix installed a strain-stress state monitoring system of “Academic Tryoshnikov” Icebreaker`s Hull. Strain sensors are welded directly to the surfaces of metal structures. Sensors applied to measure the strain of the ship hull caused by ice, waves slamming, etc. They also monitor the static operational load (during cargo transportation). As a result, it increases the operational efficiency of marine facilities. The ability to register and predict the fatigue load on certain zones helps to identify and prevent emergencies and to increase the facilities’ service life.

 

Superstructure fiber Bragg gratings (sampled SFBGs)

superstructure FBGsThe FBG structure can change with the use of the refractive index, or the grating period. The grating period can be uniform or graded, and either localized or distributed in a superstructure. The refractive index has two main features, the refractive index profile, and the decline. The refractive index can be uniform or apodized, and the refractive index decline is positive or zero.

A superstructure fiber Bragg grating (SFBG), also called a sampled fiber Bragg grating, is a special FBG that consists of several small FBGs placed in close proximity to one another. SFBGs have attracted attention in recent years with the discovery of techniques allowing the creation of equivalent chirp or equivalent phase shifts. The biggest advantage of an SFBG with the equivalent chirp or equivalent phase shifts is the possibility to generate gratings with a greatly fluctuating phase and amplitude by adjusting the spatial profile of the superstructure. The realization of SFBGs with the equivalent chirp or equivalent phase shifts requires only sub-millimeter precision.

 

Superstructure (sampled) fiber Bragg gratings (SFBGs) are good optical filters for optical communication and optical sensor systems, because of their comb-like filter response. The length of SFBG is conventionally limited by that of the phase mask. However, the length of the high-quality phase mask fabricated by an interferometric technique is limited to ~ 5 cm.  The main fabrication technique for long SFBGs based on scanning phase masks and trimming relative phases between FBGs. This technique permits to fabricate of long SFBGs with short phase masks. Superstructure fiber Bragg grating is a novel fiber Bragg grating. Because it is flexible, passive, low insertion loss, and small polarization dependent. It causes great interest and enthusiasm for the people in many areas. Ambient temperature and strain can both affect the sampled grating reflection spectrum.

 

Phase-shifted fiber Bragg gratings (πFBGs)

Phase-shifted FBGsNowadays, the special type of FBGs whose reflection spectrum has a notch arise from a π-phase discontinuity in the center of the grating (called π-phase-shifted FBGs) attracts ground interests among researchers. Because of their highly sensitive ultrasonic detection, πFBG may provide a solution to the sensitivity problems of the FBG. By introducing a π- phase shift into a refractive index modulation of the fiber Bragg grating during its fabrication, the spectral transmission has a narrow bandpass resonance appearing within the middle of the reflection lobe of the FBG. Such an element allows reaching a very narrow transmission band of few picometers.

Fabrication of π-phase-shifted FBGs is achieved by splitting the standard FBG into two identical sub-FBGs with a half-period phase difference between them. The two sub FBGs create an interfere with each other and generate an ultra-narrow transmission window at the center of the FBG spectrum.

Due to the phase discontinuity, a πFBG can be conceptually described as a Fabry–Perot cavity formed by two FBG mirrors. When the two FBGs are highly reflective, the quality factor of the Fabry–Perot cavity is increased, leading to an extremely narrow spectral notch for highly sensitive ultrasonic detection.

Using special structures, even multiple transmission bands are possible.

The primary method used for the fabrication of π-Phase-shifted fiber Bragg grating is based on the UV laser and phase mask method. The occurrence of two peaks/dips is attributed to the refractive index modulations along with the fiber core, with the periodicity of the π-phase mask that has been observed previously in images of gratings that cause destructive interference in a reflected wave at the Bragg condition owing to the phase difference between the grating phases. Thus, the standard phase mask technique produced an alternative type of pi-phase-shifted grating at twice the design Bragg wavelength.

The phase-shifted gratings have found application in distributed feedback lasers, wavelength division multiplexing, athermal setup, or temperature stabilization, as well as to a tuning setup. Also, the π-phase-shifted FBG can be used in highly accurate wavelength references, ASE filtering, spectroscopy, and optical CDMA.

 

Photonic Sensors: Technology and Applications for Safety Monitoring

Nowadays, photonics is an important part of the innovation-driven growth in an increasing number of fields. The application of photonics is distributed across several sectors: from optical data communications to imaging, lighting, and displays; from the manufacturing sector to life sciences, health care, security, and safety.

Photonic sensors have been designed for use in laboratories and industrial environments in order to detect a wide range of physical, biological, and chemical parameters. Photonics sensors can be defined as the set of techniques and scientific knowledge concerning the generation, propagation, control, amplification, detection, storage, and processing of the optical spectrum signals. In recent years, photonic sensors have been recognized as the technology that improves, extends across, and strengthens a wide variety of industrial sectors: healthcare, security, manufacturing, telecommunications, environment, aerospace, and biotechnology.

The photonic sensors market is classified generally by types and photonics applications. Type wise consist of fiber optic sensors, laser-based sensors, and biophotonic sensors. Application-wise, it is divided into construction, energy industry, oil and gas, military and aerospace, medical and industrial application. The photonic sensors market is diversified and fragmented. Photonic technology also has found a use for the industry, surgeries, and ordinary life besides its use in research laboratories.

The photonic sensors market is slowly moving from making general objectives to complicated tasks such as aircraft manufacturing applications that prescribed maximum precision. The usage of photonic sensing technology is increased in early detection and early-warning systems for biological hazards, structural flaws, and security threats. Sensors play a major role in the near future and, especially, in different photonic applications in the generation, distribution, and conservation of energy, as well as in the mitigation of the effects of energy production and consumption on the environment.

The photonic industry now is centering on the development of eco-efficient products that are projected to be developed and launched over the next few years. The need for enhanced safety and security solutions, better alternatives for conventional technology, and a rise in wireless sensing technology are some of the major factors that act as drivers for the photonic sensor market.

FBG monitoring systems for hydraulic structures

Any sophisticated construction requires constant tracking of its technical condition to detect inconsistencies between the projected calculations and the actual working parameters and to evaluate its compliance to the established standard. Currently, the most used sensors to monitor hydraulic structures are stringer transducers that perform very well under various climate conditions, especially in the areas of deep-frozen soil. However, the increasing sophistication of modern constructions is more demanding in terms of monitoring standards. Often it is no longer sufficient to use regular sensors. Hence, a new type of monitoring with fiber optic devices was created.

The length of these constructions and its complex structure demand special fiber optic devices monitor its safety. One of the most complicated constructions to place the fiber optic solutions is a hydro-electric power station. FBG sensors can be placed in the structures where regular stringer transducers fail, for example, in long shafts and tunnels. On top of that, fiber optic solutions are completely fire-safe, resistant to electromagnetic fields and radiation, and other interferences.

Tunnels in hydro-electric power stations can be equipped with the following fiber optic devices: FBG sensors for deformation, temperature, displacement, and pressure sensors. The deformation sensor is measuring the condition of the steel reinforcing, and it embedded on its surface. The sensor is covered with the isolating material to avoid the impact of the concrete. An additional temperature sensor is installed in the same location to track temperature changes that affect deformation. A displacement sensor is used to measure the joint opening between steel compression and a ram. The pressure sensor is used to measure the water pressure in the tunnel.

Optromix offers a variety of fiber optic solutions, and we will write a tailored FBG based on your specific needs.

Monitoring system for bridges

Fiber optics products can be used to monitor the condition of different bridges; it evaluates in real-time depreciation during the exploitation, provides public safety, and cuts the expenses for maintenance.

Data collected by these fiber optics products allow decreasing regular maintenance expenses of the constructions. All the information is stored in an orderly manner to enable sorting through long and short-term tracking periods. Using a monitoring system helps to use the facility in a more efficient way. Monitoring fiber optics products help to build the construction and to optimize the load in different situations, and it will make the utilization time.

The following parameters are measured with fiber optic product:

  • Relative linear beam deformation
  • Temperature next to the deformation place
  • The inclination of the supporting structure
  • Other physical dimensions

Beam sensors are located on the right and left sides of the bridge and the fiber optic product controls the pressure on the entire length of the construction, bridge conditions during the peak load and at relaxation time, relative changes in different structure elements during the exploitation period, climate changes effect.

Fiber optic product for inclination tracking controls the potential shift of the bridge over time. And the fiber optic product located at the central part of the bridge tracks the vibration and the danger of resonating frequencies.

The amount of sensors per bridge is always determined case by case. In general, it depends on the central part between the supporting structures. The part that takes the heaviest load is the central part of the bridge and it has to be measured precisely.

These sensors help to find weak parts of the structure and prevent damages and catastrophes.