fbg based Fibersensing GS6500 – COTS

This acceleration sensor is a development from fiber sensing and is named GS6500. It is available as a commercial fiber optic acceleration sensor. The functionality is similar to the FBG tube sensor, but with a different mechanical design.

The following picture gives an overview of the sensor´s mechanical design.

Two seismic masses are mounted between two Bragg gratings. The fiber is used as the spring. Another spring element is the metal film between the seismic masses. The applied acceleration acts on the seismic mass. The deviation of the mass can be acquired with the Bragg gratings.

The costs are high: about 800 Euros per sensor.

Trade criteria (properties and behavior of the sensor)

• Multiplexing ability: Yes
• Linearity: Good expectation (<1%). This sensor uses a spring mass system for the acquisition of acceleration.
• Cross sensitivity: No good expectation (<9%). This parameter depends on the mechanical layout and can be minimized for example by mechanical guidance of the moving parts.
• Resistance to shock load: No good expectation. This sensor concept can manage a shock load only up to 100g.
• Vulnerability to thermal drift: Low. The thermal drift is a problem for all optical sensor concepts. But this drift can be compensated mathematically.
• Saturation effects: None. Optical sensor concepts are not concerned about the problem of saturation effects, contrary to electrical acceleration sensors (see the page saturation effects).
• Mechanical complexity, producibility: The mechanical complexity of this sensor concept is average. The producibility is proved by the company Fibersensing which sales this sensor as a COTS product.
• Size: Medium, the dimensions are 35mm * 20mm * 20mm.
• Weight: Medium, it weighs 30 gramm.

Sensor performance requirements

• Acceleration, which implies a Measurement range of 14g, a Sensor Bandwidth > 1000 Hz and a Resolution >= 9 Bit: No. The FBG based Fibersensing GS6500 sensor cannot afford this combination of parameters that the acceleration requires.
• Vibration 1, which implies a Measurement range of 50g, a Sensor Bandwidth > 1000 Hz and a Resolution >= 9 Bit: No. The FBG based Fibersensing GS6500 sensor cannot afford this combination of parameters that the vibration 1 requires.
• Vibration 2, which implies a Measurement range of 20g, a Sensor Bandwidth > 3000 Hz and a Resolution >= 9 Bit: No. The FBG based Fibersensing GS6500 sensor cannot afford this combination of parameters that the vibration 2 requires.
• Shock load, which implies a Measurement range of 5000g, a Sensor Bandwidth > 3000 Hz and a Resolution >= 9 Bit: No. The FBG based Fibersensing GS6500 sensor cannot afford this combination of parameters that the shock load requires.

This sensor concept cannot afford any of these parameters because its Bandwidth is limited to 660 Hz.

You can make a comparison of the same criteria with other sensors using optic fiber.

• FBG – Cantilever Sensor
• FBG based waveguide sensor
• FBG tube sensor
• FBG with pivot coupling of the seismic mass

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