Self-starting, passively mode-locked Fabry-Perot fiber solitonlaser using nonlinear polarization evolution

The authors demonstrate pure self-starting mode-locked operation in a fiber Fabry-Perot cavity. The laser produces 1.6 ps transform-limited soliton pulses by means of nonlinear polarization evolution in conjunction with an intracavity fiber polarizer. This laser system can be used for the generation and study of soliton pulses in the picosecond regime. With a careful choice of the fiber dispersion and fiber length, the system should also be able to operate in the femtosecond regime. The advantage of the system over existing self-starting fiber soliton lasers is that an optical isolator (an expensive component) is not required. The replacement of the two mirrors with fiber reflection gratings would make this configuration a truly all-fiber device     

Improving feasibility of robotic milling through robot placement optimisation

Milling performed with robots is quite demanding, even for low-strength materials, due to the high accuracy requirements, the generally high and periodically varying milling forces and the low stiffness of robots compared to CNC machine tools. In view of the generally improved recently robot stiffness, it is desirable to perform the milling operation in regions of the robot’s workspace where manipulability, both kinematic and dynamic, is highest, thereby exhausting the robot’s potential to cope with the process. In addition, by selecting the most suitable initial pose of the robot with respect to the workpiece, a reduction in the range of necessary joint torques may be reached, to the extent of alleviating the heavy requirements on the robot. Two genetic algorithms (GAs) are employed to tackle these problems. The values of several robot variables, such as joint positions and torques, which are needed by the genetic algorithms, are calculated using inverse kinematics and inverse dynamics models. In addition, initial positions and poses leading to singularities along the milling path are penalized and, thus, avoided. The first GA deals solely with robot kinematics to maximize manipulability. The second GA takes into account milling forces, which are computed numerically according to the particular milling parameters, to minimise joint torque loads.     

Optical time-domain reflectometry measurements in a 4 km fibre ring laser

The first experimental Rayleigh backscatter measurements in a passively modelocked fibre ring laser are reported. The Rayleigh backscatter data were used to identify and estimate splice losses as well as the back reflection of the intracavity optical isolator.<>     

Use of an on-farm progesterone test in the clinical management of parturient disorders in three cows

Measurement of blood progesterone concentrations with a rapid, on-farm test was used to guide the clinical management of 3 cows with parturient disorders. An 8-year-old cow in the third trimester of pregnancy had chronic vaginocervical prolapse with partially dilated (4 cm) necrotic cervix. Blood progesterone concentration estimated with the test kit was low (< 2 ng/ml), and the cervical dilatation was attributed to stage-1 parturition. Vaginal delivery of the calf occurred 7 hours later. A 2-year-old cow examined for dystocia had a uterine torsion. Eighteen hours after apparent correction of the torsion, the cervix had failed to dilate. Blood progesterone concentration was 2 to 5 ng/ml, suggesting parturition had not yet been initiated. Parturition was induced with dexamethasone and prostaglandin, and calving occurred 32 hours later. A pregnant, 16-month-old heifer was believed to be about to calve and was admitted because of potential need cesarean section. Examination revealed the cervix to be closed. Blood progesterone concentration was low, and calving was predicted to occur within 24 hours. The heifer was monitored, and stage-2 labor was observed 8 hours later. The calf was delivered with minor assistance. In each case, the test provided diagnostic information that was useful in making therapeutic management decisions.     

Selfstarting passively mode-locked fibre ring soliton laser exploiting nonlinear polarisation rotation

Nonlinear birefringence effects in a fibre ring laser cavity have been exploited to produce selfstarting, passive mode-locking to give 1.5 ps soliton pulses.<>