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Announcements - Intrinsic transducer

Paper - Photonic bandgap Bragg fiber sensors for bending/displacement detection

posted Aug 30, 2013, 9:47 AM by Tiberius Brastaviceanu   [ updated Aug 30, 2013, 9:50 AM ]

SENSORICA members in collaboration with Maksim Skorobogatiy and Hang Qu, from Ecole Polytechnique de Montreal.

Zemax simulation of MM fiber bending loss

posted Aug 23, 2013, 10:32 AM by Tiberius Brastaviceanu   [ updated Aug 23, 2013, 10:34 AM ]

Recently, Hang Qu used Zemax to simulate the fiber bending sensor based on a regular multimode fiber. Here are some of his conclusions:


  • Zemax is capable to simulate the bending sensing based on a regular multimode fiber, optimize the optical configuration of the fiber sensor setup (collimating light sources, optimizing coupling efficiency of fiber), calculate the transmission or reflection intensity of fiber in response to bending.
  • In the simulation, the mirror can be either coated on the end of fiber, or you can also use external mirror which put in the vicinity of the fiber free end.
  • in the simulation, the fiber tip can be cleaved vertical to the fiber axis, or with an angle tilted to fiber axis.
  • Zemax can not directly simulate the fiber with scratches, however, one can instead add an absorption layer coated on the core of the fiber to simulate these scratches.
  • Zemax can calculate the coupling efficiency of single mode fiber or fiber taper, but have difficulties in simulating the transmission or reflection intensities of single mode fiber or tapered fiber. Because zemax operates by ray tracing, when the core size is large (e.g. multimode fiber), you can approximate use ray tracing and total internal reflection principle to simulate the guidance of fiber. However, when the core size is small (e.g. single mode fiber), you have to use modal analysis to calculate the behavior of fiber. Therefore, for bending sensor based on tapered fiber, I think comsol (3D simulation) would be a better option.


The attachment is some figures for the simulation of the bending multimode fiber with the fiber tip coated with a mirror. If you guys want to use Zemax in you simulation in the future, I am willing to share my opinions.

First results with the bragg fiber

posted Jan 22, 2013, 7:38 PM by Sensorica Group   [ updated Jan 22, 2013, 7:41 PM by Tiberius Brastaviceanu ]

Hang, working from his lab at the Ecole Polytechnique de Montreal, obtained the first conclusive results for the intrinsic bend-sensitive optical fiber. This optical fiber has immediate applications in robotics (see Robot finger project).

Experimental setup used in this experiment

By Hang: A simple description of the experimental setup is given as follows: the light from supercontinuum (coming from the hole on the black box) goes through the beam splitter and is coupled to the Bragg fiber by a 20× objective. Then the light is reflected back by the silver mirror on the other end of the Bragg fiber, collimated by the same objective and projected to the beam splitter and detector. A nano-position stage is used to bend the silver-coating end of the Bragg fiber.  A black absorber is used to block the supercontinuum beam directly reflected by the input facet of the Bragg fiber. This reflection at the fiber input end could form a very bright, tiny spot due to the focusing by the objective and the reflection is insensitive to bending such that it will only constitute noise to the detector. With this setup, we are able to measure the intensity variations in response to the different bending of the Bragg fiber.

By Hang: The reflection of a 300-micron diameter 4-cm long Bragg fiber is measured in response to different bending radius. The bending of fiber is enabled by a nano-position stage which is used to bring the displacement to the fiber tip coated with a silver mirror [using Francois's technique for wet silver coating]. The reflection intensity is real time accompanied by the bending of the fiber. The displacement is noted in the figure below.

The input light is wight coherent light generated from a powerful fs laser, pumping a continuum generation crystal.


By Hang: I found that with the 300 micron-diameter 4cm-long fiber, the minimal displacement that can be reliably detected is ~0.5mm

Further steps
We now need to find the wavelength at which this optical fiber is most sensitive, and filter it our of the input light, or before the detection. This will increase the sensitivity of the device.

Work must be done on signal conditioning.

Smaller fiber diameters will be tested next week, starting with 100 micron.

Project is starting

posted Nov 22, 2012, 4:15 PM by Tiberius Brastaviceanu   [ updated Nov 22, 2012, 6:37 PM ]

We are getting ready to perform the first tests on some polymer bandgap fibers. 

Ordered the (330micron and 125micron inner diameter) connectors for polishing the fiber about two weeks ago; however, we have not received them yet. We expect we would receive them this week or early next week). Last week we tried to use the 400micron-diameter connector to polish the 300micron-diameter Bragg fiber (we only have connector with diameter larger than 400micron). The polishing was not perfect due to the incompatibility between the connector and the fiber.

As an example, the typical facets of the Bragg fiber after polishing are shown in the figure attached here. Though some scratches and small speckles can be seen on the facets, they would no affect the performance of the Bragg fiber used as a bending sensor. Note that the polishing will be improved after we receive the new fiber connectors.
Mainly contributed by Hang

ENGAGE grant was awarded!

posted Oct 15, 2012, 6:43 PM by Tiberius Brastaviceanu   [ updated Oct 15, 2012, 6:43 PM ]

A $25,000 grant was awarded on Oct 5th, 2012. The goal of this project is to design new optical fiber displacement/force transducers. See grant application - members only. See past funding.  

Maksim runs a state-of-the-art photonics/optics lab at Ecole Polytechnique de Montreal, with very expensive and exotic equipment. Access to this lab represents a very important asset for SENSORICA.

Long-term targets: biochemical sensors

Picture from Maksim's website.

Ecole Polytechnique accepted to transfer the ENGAGE grant application to NSERC

posted Aug 28, 2012, 5:29 PM by Tiberius Brastaviceanu   [ updated Aug 28, 2012, 5:29 PM ]

The Ecole Polytechnique accepted to transfer the ENGAGE grant application to NSERC. Good news ! This is the second hurdle cleared for obtaining this grant, which will be used for developing a series of intrinsic displacement/force transducers, in collaboration with Maksim. 

ENGAGE grant - moving forward

posted Aug 4, 2012, 5:37 AM by Tiberius Brastaviceanu   [ updated Aug 4, 2012, 5:37 AM ]

François Santerre, our contact at NSERC, gave us the green light to submit our ENGAGE grant proposal with Maksim Skorobogatiy for the development of other types of force-sensitive optical fibers. Francois, Tibi and Philippe are driving this initiative. 

ENGAGE proposal - resent

posted Jul 4, 2012, 4:38 PM by Tiberius Brastaviceanu   [ updated Jul 12, 2012, 9:44 AM ]

Towards the end of June, Francois made corrections to the proposal and sent it back to Santerre for revision. We are waiting for a reply. The grant will be re-evaluated after July 23rd.

ENGAGE proposal - needs to wait

posted Jun 17, 2012, 10:33 AM by Tiberius Brastaviceanu   [ updated Jun 17, 2012, 10:33 AM ]

We got some feedback for our proposal before submission, and we were advised to wait until we get some data from Philippe's project (also funded with an ENGAGE grant) before we submit, in order to increase our chances of success. This grant went through Tactus, in collaboration with Philippe. The problem is that Tactus was only created last year, which plays against our chances, especially when we factor in the fact that we were already granted an ENGAGE, and the maximum allowed per year is two. 

ENGAGE proposal - editing the draft

posted May 8, 2012, 1:15 PM by Tiberius Brastaviceanu   [ updated May 8, 2012, 1:15 PM ]

We already started to edit the draft of the ENGAGE proposal we are submitting with Maksim. Tibi and Maksim are the two lead authors. The submission date is the end of May 2012. 

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