A single-fiber forward transmission distributed vibration sensor (SF-FTDVS) is proposed in this article based on bi-directional structure, which breaks the dependence of traditional FTDVS on the interference loop structure or the multifiber optical path. The proposed SF-FTDVS inherits the advantages of fiber sensors with forward transmission. It can realize the relay-free distributed vibration sensing greater than 210 km since the continuous forward transmission of light waves provides good signal-to-noise ratio (SNR) performance. Besides, the bidirectional transmission structure enhances the consistency of vibration event perception, so that it can achieve a more precise location. Experiments demonstrated the feasibility of vibration event location with a wide-frequency range from 400 Hz to 10 kHz, allowing for an un-repeated sensing link up to 212 km. To the best of our knowledge, this represents the longest perception distance achieved by a relay-free sensor. The average location standard deviation (STD) and the location fluctuation range are estimated to be 15.7 m and ±37 m, respectively, demonstrating an improvement of 14% and 12% compared to the traditional distributed vibration sensors (DVS) scheme. The proposed SF-FTDVS not only offers the advantages of simple deployment, high-positioning accuracy, and wide vibration response bandwidth, but also exhibits good compatibility with other components, demonstrating great potential for applications in Internet of Things (IoT) systems.

Accurate haptic feedback is a critical challenge for surgical robots, especially for flexible endoscopic surgical robots whose transmission systems are Tendon-Sheath Mechanisms (TSMs) with highly nonlinear friction profiles and force hysteresis. For distal end haptic sensing of TSMs, this paper, for the first time, proposes to measure the compression force on the sheath at the distal end so that the tension force on the tendon, which equals the compression force on the sheath, can be obtained. A new force sensor, i.e., a nitinol tube attached with an optical Fiber Bragg Grating (FBG) fiber, is proposed to measure the compression force on the sheath. This sensor, with similar diameter and configuration (hollow) as the sheath, can be compactly integrated with TSMs and surgical end-effectors. In this paper, mechanics analysis and verification tests are presented to reveal the relationship between the tension force on the tendon and the compression force on the sheath. The proposed force sensor was calibrated in tests with a sensitivity of 24.28 pm/N and integrated with a tendon-sheath driven grasper to demonstrate the effectiveness of the proposed approach and sensor. The proposed approach and sensor can also be applied for a variety of TSMs-driven systems, such as robotic fingers/hands, wearable devices, and rehabilitation devices.

The problem of dynamic multicast routing and wavelength assignment (MC-RWA) in the wavelength-routed wavelength-division-multiplexing networks is addressed. Current solutions to this problem always rely on homogeneous network constructions. However, future backbone networks tend to be heterogeneous in nature. Thus, the dynamic MC-RWA problem should be studied in a more realistic situation by considering the heterogeneity of network structures. A new graph model is proposed for the MC-RWA problem. This model is based on layered auxiliary graph which is generic and able to support various node architectures and heterogeneous network structures. Based on this graph model, the dynamic MC-RWA problem can be simply solved by an efficient multicast tree algorithm on various light-splitting and wavelength-conversion scenarios. In general, this graph model provides a universal platform to study different aspects of the dynamic MC-RWA as well as related problems.

A novel channel-allocation method that allows reduction of the four-wave mixing (FWM) effect while maintaining bandwidth efficiency is presented. It is composed of a fractional bandwidth-allocation algorithm, taking into consideration the use of parameters with distinct differences. This proposed technique allows the computation of an optimal channel-allocation set, where degradation caused by interchannel interference and FWM is minimal. Simulation is carried out to show significant performance improvement, such as an average bit-error rate improvement factor of 1.336 for an eight-channel wavelength-division multiplexing system, without the requirement of increased bandwidth, unlike existing channel-allocation methods.