Fig. 3. The resonant waveform in the fiber analogue setup
combine the SSR and the light together in one element by doping the
optical waveguide to form an active SSR.
In 1997, the task to develop an active SSR was difficult to be completed,
we had to use separately the passive SSR and the light source with
extremely narrow linewidth.
Firstly, a high power 25 mW Nd-YAG laser was used in the setup and
the measured finesse of the passive SSR is around 35–40. According to the
measured finesse, the linewidth of the Nd-YAG laser has been calculated
as around 240 kHz. This value coincides with the real linewidth of the
Nd-YAG laser.
Considering that the Nd-YAG laser is not suitable to be used in the
MOG product, we have developed a fiber Bragg grating FBG-LD with
narrow linewidth. As shown by the measured result, the linewidth is around
1.5 MHz.
The FBG-LD was used in the setup for replacing the Nd-YAG laser. As
shown in the resonant waveform in the SSR (Fig. 3), the actual finesse of
SSR is about 20–25. Obviously, the linewidth of the light source reduced
the finesse of SSR significantly.
In comparison with the resonant system configuration, the proposed
interferometer system configuration is easier to be realized on the base of
the matured elements, used in IFOG, including the light source SLD, the
MIOC, and the closed loop control electronics.
For developing the MOG with higher accuracy, in both system
configurations, the active waveguide SSR is necessary to be used, because
in the proposed interferometer system configuration, the number of round
trips of light beams in the passive SSR is
<
5
.
Conclusions. 1. In the near future, the proposed re-entrant interferometer
system configuration with passive SSR is feasible for the development of
the MOG with moderate accuracy. This kind of MOG is realistic to be
developed, because the elements of the MOG are compatible with those
used in IFOG, which are matured industrial products.
ISSN 0236-3933. Вестник МГТУ им. Н.Э. Баумана. Сер. “Приборостроение”. 2005. № 4 115
