utilising compact
design, affordable manufacturing methods and a mixture of superalloys and high-expansion materials to achieve the desired
operating parameters.
The predicted stability of the system over a -40°C, +70°C is shown in the accompanying figures. The modelled
stability has been derived taking into account the non-linear behaviour of the compensating materials. The predicted
behaviour is calculated from the formula:
With:
Dl/l = change in wavelength as a function of the original wavelength
afibre = coefficient of linear thermal expansion of the fibre
x = The thermo-optic coefficient
DT = change in temperature in °C
re = photoelastic constant
De = change in strain
And for the example given:
l = 1550nm
afibre = 0.55 E-6 /°C
x = 6.9 E-6 /°C
re = 0.22
The compensating package will exhibit a discontinuity in the performance when (1 -
re).De
= 0 and the grating reacts to changes in temperature. The temperature at which this occurs is specifiable, within a total
range that is dependent upon the performance required.
The package is to be certified to Bellcore / Telecordia GR 1221 Core, vibration, shock and cable retention. Hermetic sealing can be arranged. The package is designed to allow ease of installation of the FBG, with fine tuning possible when installation of the Bragg grating is completed.
Performance:
The calculated drift originating from the package is:
Size:
For a 25mm Bragg grating length the following external package dimensions are available, for a basic unit with strain relief,
excluding strain relief boots.
Overall lid and base unit excluding strain relief spouts: 14 x 9 x 61mm
Strain relief boots are shown (3), with the base fixing attachment (8), the compensator (2), the external package (1) and lid unit (4) and strain relief method (5). Buffered fibre is shown (6).
For more details, contact us.
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