| 摘要 |
Two portions (B,C) of one arm of an optical fibre Mach-Zehnder interferometer are magnetically sensitized and each has applied thereto an a.c. bias fields at a respective different frequency (w1, w2). One portion (A) of the other arm of the interferometer is magnetically sensitized and has two a.c. bias fields applied thereto, each at one of the different frequencies (w1,w2). The fields for portion A and C are aligned with a first direction (x) whereas those for A and B are parallel, A and B being separated in a second direction (y). The detected output of the interferometer at frequency w1 is related to the magnetic gradient in the y direction, whereas the detected output at frequency w2 is related to the magnetic gradient in the x direction. Thus using two bias frequencies allows one interferometer to be used to detect two gradients (FIG. 8).
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