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Frequently Asked Questions

Welcome to the frequently asked questions page for Sengenia. We hope that you’ll find an answer to your enquiry here but if not please don’t hesitate to contact us via any of the means listed on our contacts page.


The page is divided into 3 sections: 


Q: What is the maximum distance that there should be between the sensor and the interrogation system?
A: The maximum distance from the interrogation system to the sensors is dependent on the loss of your fibre cable. A typical cable loss is estimated to be 0.5dB/km loss, two way.

Q: What can you tell me about using the FBGs in cryogenic conditions?

A: In general, cryogenic temperature sensing using FBGs is possible and has been done by various groups. For cryogenic strain sensing by far the most common tends to be the use of bare, polyimide coated fibres mounted on the specimens of interest. In this sense, the grating will measure both the strain and temperature, except that - depending on the cryo temperature - the expected strain and temperature wavelength shift coefficients will tend to be different that those normally used at room temperature. Our os3100 will not work at cryo, because of the pre-stretch. However, our os3200 should be fine, except that the appropriate low temperature epoxy must be used. So, in a nut shell, use os1100s or os3200s with polyimide coating and use suitable epoxies.

Q: What conditions are used for the temperature calibrations?

A: We use our Hart temperature readouts and probes for calibrating our temperature sensors. They are calibrated (as a pair) once per year to a NIST traceable standard through a local calibration company.

Q: What is the primary coating of the fibre used for the 120 degree and 275 degree versions of the os4310?

A: Both versions use polyimide coating

Q: The gratings provided, are they draw tower produced?

A: No, however we can supply Draw Tower Gratings from a trusted supplier, please get in touch and we would be happy to help you source these. 

Q: Do you know if the sensor metal base could be bent (e.g. os3120)?

A: No. These sensors are designed for flat surfaces. It would make the measurement unreliable and the calibration constants would change. You might want to try using the os3200 sensor for a curved surface. It is non-metallic and is designed to apply an even amount of epoxy around the FBG and to the surface you want to monitor.

Q: Is the fibre in the groove bonded or pre-stressed for the packaged sensors?

A: The fibre is pre-stressed and then bonded between two points on the metal base.

Q: What temperature sensor would you recommend for higher pressure environments?

A: The most important factor with the different pressures is the compression fitting seal on the stainless steel housing of the temperature sensor. We have never really reached a pressure ceiling, so they haven’t necessarily been certified for use in specific environments. Our engineers recommended the os4230 and os4280 as this is a rugged probe in stainless steel housing about 3/16” and 1/4" wide.

Q: Are there any issues to using the sensors for monitoring marine turbines?

A: So long as proper waterproofing of the carrier and cable are taken into consideration, there shouldn’t be any major obstacles.


Interrogation Systems

Q: What does the “sm” and “si” mean in the unit names?
A: Each interrogator is either a sensing module, "sm," or sensing instrument, "si." Sensing modules (e.g., sm125) respond to user commands for data transfer via an Ethernet connection. Sensing Instruments use Integrated ENLIGHT and Embedded XP for onboard management of the interrogator core settings, data management, sensor calibration, data visualization and data storage. User interaction is via an external keyboard/mouse/monitor or built in touch screen.

Q: Are the sm125 and sm130 units still available?
A: No, these items are now discontinued, however there will occasionally be refurbished systems available, contact us to find out more. 

Q: I’d like to customize the front end of the interface to the interrogator. From the manual it appears I can interface with LabView but wondered if there is provision for me to write an application in something like C# (.net) and send commands to the interrogator?
A: Any programming language can be used to talk to the interrogator, including C#. As long as one follows the same sort of steps, procedures and string command structure as described in the ENLIGHT manual, you should be able to communicate with the instrument. LabView would be the easiest way since we already have routines that come with the instrument and National Instruments has more routines written for our instruments available off their web site.

Q: Can any Ethernet cable be used with the units?
A: We supply crossover cables with the units as a standard Ethernet cable will not function properly.

Q: Is there a simple way that I can view the IP address?
A: You can view the IP address by booting the system when VGA monitor is connected. Then adjust the IP address accordingly. See section 5.1.1 in the user manual for more detailed information.

Q: Is ENLIGHT Mac compatible?
A: ENLIGHT software can only be run on Windows, however, there are plenty of workarounds to have Mac OS and Windows on a single Mac machine.

Interrogation Systems


Q: What is the max input power for FFP-TF2 having 10000 finesse?
A: The maximum input power is based on various experimental input. There is no rigorous theoretical basis for our numbers. The key parameter is the intra-cavity re-circulating power, which is the input average power divided by the mirror transmission. Often we have ~20W of intra-cavity re-circulating power in our swept lasers. So for a mirror R~99.9% (T~0.001) the average input power is ~20mW.

Q: Could you clarify if your FFP filters reflect the light back at the wavelengths being out of the filter bandwidth or not? If your filter is just a usual Fabry-Perot interferometer, it should reflect the light back, am I right?
A: Correct, all wavelengths that make it through the transmission window are reflected.

Q: Can we tune wavelength and keep the FSR, i.e. we just shift the peaks, or the tuning changes the FSR only i.e. the peak spacing is varied?
A: The FSR is maintained while tuning the filter. The mirror ferrules within the filter are held in place with PZT. For the FFP-TF, increasing the voltage to the PZT forces the mirrors apart and lengthens the etalon cavity therefore moving the peaks towards longer wavelengths. More technical information can be found under the general overview section of the Tunable Filter Document Library on the Micron Optics website.

Q: Do you have a 400 GHz filter(any type)?
A: A 400GHz can be achieved with both the FFP-I and FFP-TF2.

Q: I’m interested in the FFP-TF and wondering if Micron Optics can offer pigtailing the filters with PMF on input and output?
A: It may be possible, but it adds a considerable cost to use PMF.

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