Design And Development of A 6-Port Optical Circulator Using Silicon Photonic Crystals

A 6-port optical circulator using silicon photonic crystals has been designed and proposed in this paper as an essential component of an optical communication system. The proposed 6-port circulator has greater isolation loss values between the input and isolated ports and lower insertion loss values between the input and output ports. The proposed circulator achieves maximum isolation of -38.7 dB and minimum insertion loss of 0.0029dB. The proposed designs are extremely useful in the telecommunications industry, wavelength division multiplexing and photonic integrated circuits applications due to their low insertion and high isolation losses.

Magnetless Optical Circulator Based on an Iron Garnet with Reduced Magnetization Saturation

A three-port circulator for optical communication systems comprising a photonic crystal slab made of a magneto-optical material in which an magnetizing element is not required to keep its magnetic domains aligned is suggested for the first time. By maximizing the incorporation of europium to its molecular formula, the magneto-optical material can remain in the saturated magnetic state even in the absence of an external DC magnetic field. Two- and three-dimensional simulations of the device performed with full-wave electromagnetic solvers based on the finite element method demonstrate that, at the 1550 nm wavelength, the insertion loss, isolation, and reflection levels are equal to or better than −1 dB, −14 dB, and −20 dB, respectively. Since its operation does not require an electromagnet or a permanent magnet, the suggested circulator is much more compact, being able to reach footprints in the range of three orders of magnitude smaller, when compared to other circulator designs referred to in the literature and the presented results can be useful for the design of other nonreciprocal devices with reduced dimensions for optical communication systems.

Research on technology of 1550nm all-fiber continuous wave coherent Doppler wind lidar

In order to obtain the telemetry data of wind field 80 m ahead of the wind turbine, an all-fiber continuous wave coherent Doppler lidar (CW-CDL) system is demonstrated in this paper. The CW-CDL of all-fiber structure has advantages of the compact structure, good stability and low cost. However, there is inherent crosstalk in the optical circulator of the optical fiber module, the crosstalk light and the reference light enter the photon detector together to produce phase induced intensity noise (PIIN). Aiming to effectively solve the noise, we proposed a polarization control method by combining a polarization beam splitter and a quarter wave plate to reduce the PIIN in the system. The wind speed Doppler signal at 80 meters is obtained on a sunny day, and the typical signal-to-noise ratio can reach 21.7 dB.

Distributed acoustic sensing of subsea wells

Topside distributed acoustic sensing (DAS) of subsea wells requires advanced optical engineering solutions to compensate for reduced acoustic bandwidth, optical losses, and back reflections that are accumulated through umbilicals, multiple wet- and dry-mate optical connectors, splices, optical feedthrough systems, and downhole fibers. To address these issues, we introduce a novel DAS solution based on subsea fiber topology consisting of two transmission fibers from topside and an optical circulator deployed in the optical flying lead at the subsea tree. This solution limits the sensing fiber portion to the downhole fiber, located below the subsea tree, and enables dry-tree-equivalent acoustic sampling frequencies of more than 10 kHz while eliminating all back reflections from multiple subsea connectors above the tree. When combined with enhanced backscatter single-mode fiber, this gives rise to a DAS interrogation system that is capable of providing dry-tree-equivalent acoustic sensing performance over the entire length of the subsea well, regardless of the tie-back distance. It also enables the same spectral-based DAS processing algorithms developed for seismic, sand control, injector/producer profiling, and well integrity on dry-tree wells to be applied directly to subsea DAS data. The performance of this subsea DAS system has been validated through a series of laboratory and field trials. We show the results of the tests and discuss how the system is deployed within subsea infrastructure.

A Novel Architecture of N × N Bidirectional Reconfigurable Multiwavelength Optical Cross Connect

A novel architecture of N×N bidirectional-reconfigurable multiwavelength optical cross connect (B-RMOXC) based on tunable Fiber Bragg grating and optical circulator is proposed. B-RMOXC network is one of crucial network element for wavelength routing in dense wavelength division multiplexing system. This paper presents a high speed, power compensated bidirectional optical cross connect and verified the performance of bidirectionality with 0.8-nm channel spacing having bit rate of 10 Gbps at different transmission distances. Optical signal-to-noise ratio of 36.62 dB and 35.55 dB is achieved with acceptable Quality factor of 6.26 and 6.99 respectively for upstream and downstream at 60 km having input transmission power of −12 dBm. It is found that the data can be communicated bidirectionally to a distance of 60 km in the presence of fiber nonlinearities without optical amplifier.