A novel lensed fiber for side-coupling of a single-mode(SM) optical fiber and the corresponding fabrication method were
proposed, which makes the coupling assembly more compact and easy to integrate and package. The novel lensed fiber
mainly composes of a portion of SM optical fiber and a portion of coreless optical fiber. The two fibers are jointed by
fusing splicing. The end of the coreless fiber is shaped to have a 45 degree angled end face and polished to form a
contoured curved surface. Then the contoured surface is coated so it acts as a curved reflective surface. Besides, the
cylindrical surface of the coreless fiber acts as a second curved surface. The two curved surfaces compose a pair of
equivalent cylindrical lens. After being focused by the equivalent cylindrical lens pair, the output spot size is comparable
to the mode field radius of the SM optical fiber. Matrix optics was used to analyze the output beam parameters of the
proposed lensed fiber structure. Simulation results showed that the proposed lensed fiber can bend the beam with 90
degree and make a focused spot on its side with a small spot size close to 6µm, which is suitable for fiber to
photodetector chip side-coupling applications.
A precision centrifuge is used to test and calibrate accelerometer model parameters. Its dynamic unbalance may cause the
perturbation of the centrifuge to deteriorate the test and calibration accuracy of an accelerometer. By analyzing the
causes of dynamic unbalance, the influences on precision centrifuge from static unbalance and couple unbalance are
developed. It is considered measuring and balancing of static unbalance is a key to resolving a dynamic unbalance
problem of precision centrifuge with a disk in structure. Measuring means and calculating formulas of static unbalance
amount are given, and balancing principle and method are provided. The correctness and effectiveness of this method are
confirmed by experiments on a device under tuning, thereby the accurate and high-effective measuring and balancing
method of dynamic unbalance of this precision centrifuge was provided.
The determination of unobservable states is important in consideration of system performance during initial alignment.
The aim of observability analysis is concluded as follows: 1) finding the observable states or linear combinations of these
states; 2) finding those states whose measurements turn the system into a completely observable; 3) separating the
system into observable and unobservable subsystems. In this paper, the system equation and measurement equation of
SINS for Kalman filtering are given. The Observability of initial alignment process of SINS is analyzed by means of
singular value decomposition method. Degree of observability for every state can be computed by preceding method, the
three unobservable states of INS are obtained; therefore optimal observable subspace is determined by structure
decomposition method. For proving the correctness and effectiveness of this proposed method, a Kalman filter is
designed. The Kalman filtering results are obtained. By comparing these results with results of observability analysis, the
uniform conclusion is obtained. Before designing a Kalman filter, the observability of every systematic state can be
known by use of the singular value decomposition method of the observable matrix, i.e. degree of observability for every
state can be computed. Therefore observable vector and optimal observable subspace may be determined. The
correctness and effectiveness of this proposed method was proven by analyzing results of Kalman filtering. This method
can be used for direct design of a Kalman filter.