Real-Time 4-Mode MDM Transmission Using Commercial 400G OTN Transceivers and All-Fiber Mode Multiplexers

Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.

Research on the Long-distance Transmission

In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It mainly analyzed two ways of the long-distance transmission: UHV AC transmission and UHV DC transmission. The fractional frequency transmission technology and half wavelength AC transmission technology of AC transmission are introduced. Some key technologies of long-distance transmission are described. It has a guess for long-distance transmission future direction.

Research on the influence of ocean temperature on XCTD profiler single-mode fiber transmission channel

XCTD, as one of the most important instruments for the deep sea exploration, is an important device for deep-sea hydrological data acquisition. But some difficult technical problems of traditional metal enameled wire channel have become the major bottleneck for XCTD development. Aiming at this problem, this paper puts forward with using single-mode fiber as the transmission channel of XCTD. Firstly, this paper makes a brief analysis on the problems of using enameled wire as transmission channel faces. Secondly, it analyzes the advantages of the single mode fiber technology. Finally, it makes theoretical research and experimental verification of the influence of seawater temperature change on the optical fiber transmission channel. The experimentat results show that the error rate at the transmission rate of 10 MB/S is 0, and the loss can be negligible when the single-mode fiber channel is used in the sea water and the seawater temperature changes from 0 to 20℃. This method will greatly increase the rate of signal transmission and the transmission stability. And this paper shows that using the single-mode fiber as the transmission channel of XCTD has certain feasibility.

Design and Realization of Phased Array Radar Optical Fiber Transmission System

One optical fiber transmission system is designed. The modularization optical fiber transmission adapters were utilized in the system, so the system structure could be flexibly sealable. The sub-array adapter and signal processor adapter were designed and realized utilizing the new field programmable gate array （FP- GA） which could drive the optical transceiver. The transmission agreement was designed based on the data stream. In order to solve the signal synchronization problem of the optical fiber transmitted phased array radar, a method named synchronous clock was designed. The fiber transmission error code rate of the system was zero with an experimental transmission velocity of 800 Mbit/s. The phased array radar system has detected the airplane target, thus validated the feasibility of the design method.

Fiber Bragg grating monitors for thermal and stress of the composite insulators in transmission lines

Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating(FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.

Influence of intra-cavity loss on transmission characteristics of fiber Bragg grating Fabry–Perot cavity

A theoretical model of the fiber Bragg grating Fabry–Perot（FBG-FP） transmission spectrum considering loss of FBG and intra-cavity fiber is presented. Several types of FBG-FPs are inscribed experimentally, and their spectra are measured.The results confirm that weak intra-cavity loss is enhanced at the resonance transmission peak, that is, loss of transmission peaks is observably larger than other wavelengths. For FBG-FPs with multi resonance peaks, when the resonance peak wavelength is closer to the Bragg wavelength, the more significant loss effect of resonance transmission peak is exhibited.The measured spectra are fitted with the presented theoretical model. The fitted coefficient of determinations are near 1,which proves the validity of the theoretical model. This study can be applied to measure FBG loss more accurately, without a reference light. It can play an important role in FBG and FBG-FP writing process optimization and application parameter optimization.

Effect of Overlaid Material on Optical Transmission of Side-Polished Fiber Made by Wheel Side Polishing

The performance of optical power transmission through a side-polished fiber on which materials of different refractive indices were overlaid is investigated. The experiments show that the transmitted optical power through the side-polished fiber varies with the refractive index of the overlaid material. The result of our experiments fits well the theoretical calculation. Side-polished fiber manufactured by wheel polishing method can be used not only to control optical power transmission through the fiber core but also as a refractive index sensor.

Efficient reference-less transmission matrix retrieval for a multimode fiber using fast Fourier transform

Imaging through multimode fiber(MMF)provides high-resolution imaging through a fiber with cross section down to tens of micrometers.It requires interferometry to measure the full transmission matrix(TM),leading to the drawbacks of complicated experimental setup and phase instability.Reference-less TM retrieval is a promising robust solution that avoids interferometry,since it recovers the TM from intensity-only measurements.However,the long computational time and failure of 3D focusing still limit its application in MMF imaging.We propose an efficient reference-less TM retrieval method by developing a nonlinear optimization algorithm based on fast Fourier transform(FFT).Furthermore,we develop an algorithm to correct the phase offset error of retrieved TM using defocused intensity images and hence achieve 3D focusing.The proposed method is validated by both simulations and experiments.The FFT-based TM retrieval algorithm achieves orders of magnitude of speedup in computational time and recovers 2286×8192 TM of a 0.22 NA and 50μm diameter MMF with 112.9 s by a computer of 32 CPU cores.With the advantages of efficiency and correction of phase offset,our method paves the way for the application of reference-less TM retrieval in not only MMF imaging but also broader applications requiring TM calibration.

Nonconvex optimization for optimum retrieval of the transmission matrix of a multimode fiber

Transmission matrix(TM)allows light control through complex media,such as multimode fibers(MMFs),gaining great attention in areas,such as biophotonics,over the past decade.Efforts have been taken to retrieve a complex-valued TM directly from intensity measurements with several representative phase-retrieval algorithms,which still see limitations of slow or suboptimum recovery,especially under noisy environments.Here,we propose a modified nonconvex optimization approach.Through numerical evaluations,it shows that the optimum focusing efficiency is approached with less running time or sampling ratio.The comparative tests under different signal-to-noise levels further indicate its improved robustness.Experimentally,the superior focusing performance of our algorithm is collectively validated by single-and multispot focusing;especially with a sampling ratio of 8,it achieves a 93.6%efficiency of the gold-standard holography method.Based on the recovered TM,image transmission through an MMF is realized with high fidelity.Due to parallel operation and GPU acceleration,our nonconvex approach retrieves a 8685×1024 TM(sampling ratio is 8)with 42.3 s on average on a regular computer.The proposed method provides optimum efficiency and fast execution for TM retrieval that avoids the need for an external reference beam,which will facilitate applications of deep-tissue optical imaging,manipulation,and treatment.

Influence of Laser Phase Noise on Nonlinear Optical Fiber Transmission System

he influence of laser linewidth on optical fiber transmission systems has been investigated. The maximum transmission distances at different linewidths are first calculated in linear systems with various bit rates. Then it is found that SPM can significantly enhance the PMAM noise which severely deteriorates the performance of system with high optical power and large dispersion. In this case, the laser linewidth and optical power must be well controlled.

2.4Gb/s,50Km Optical Fiber Transmission Using Ti:LiNbO_3 External Modulator

2.488 Gb/s optical fiber transmission experiment using a domestic Ti.LiNbO3 externalmodulator was demonstrated for the first time in China.A receiver sensitivity of -30.3dBmwas obtained at a BER of 10-10after transmission through 50.7 km conventional single modefiber.

Experimental Study on Stimulated Brillouin Scattering Effect in Single Mode Fiber Transmission System

timulated Brillouin Scattering(SBS), one of the important nonlinear optical effects in optical fiber transmission systems, was systemically studied by experiments. The relationship of SBS threshold characteristic with linewidth of light source and modulation formats was discussed, and approved by experiments. The effect of SBS on bite error rate characteristic of the system was also investigated experimentally.

Analyzing the Location of the Transmission Windows in Phase-shifted Fiber Grating

Using the matrix approach,we analyzed the relation between the location of the transmission in stop band and the phase shift,and discussed the problem of varying the bandwidth of the transmission window.These theoretical results in this paper have important significance for actual application of the phase-shifted fiber grating.

Transmission Properties of Fiber Probes

Transmission properties of tapered fiber including right cone fiber and bend optical fiber are discussed.The transmission efficiency of the tapered fiber is measured.The curve of transmission efficiency versus taper cone angle is given.By the scalar wave equation and Gaussian approximation,transmission properties of the two kinds of tapered fibers are analyzed,the power losses caused by taper cone angle and by the bending are also calculated.From the experiments and theoretical analysis,it could come to a conclusion that the wider the taper cone angle is,the higher the transmission efficiency will be.

Two Schemes for a Soliton Transmission with Er^(3+) -doped Fiber Amplifier

This paper shall propose two schemes for soliton transmission with Er3+ doped fiber amplifier(EDFA). To compared with second scheme, The first scheme will most likely be dominant.

Numerical Study on Optical Solitons Transmission System with 40 Gbit/s in the Photonic Crystal Fiber

The 40 Gbit/s optical solitons transmission system in photonic crystal fiber was investigated by fast Fourier transform method, and the maximum transmission distance of system was calculated numerically. By the eye pattern of system, the transmission performances of system were studied. Results show that when polarization mode dispersion coefficient Dp is smaller than , the influence of the PMD on the transmission distance was neglectable. When the dispersion coefficient D is larger than 1.5 ps/km/nm, the transmission distance decreases rapidly. The positive or negative of three order group-velocity dispersion makes no differences on the system transmission.

Transmission Restriction and Suppression of Radio over Fiber Communication System

This article puts forward long-reach and high-performance Radio over Fiber (RoF) Communication Systems.Two schemes are proposed for solving the transmission restriction factors of the RoF system and verifies the system through experiments.One scheme is 40GHz RoF system based on external modulation with odd-order sideband-suppressed.The other one is 40GHz Optical Frequency Division Multiplexing (OFDM) system based on Optical Carrier-Suppression (OCS),external modulation.Both theory and experiment prove that the two systems allow not only low chromatic dispersion,but also long-distance transmission.

High Speed VCSEL-Based Parallel Optical Transmission Modules

Design and fabrication of a parallel optical transmitter are reported. The optimized 12 channel parallel optical transmitter,with each channel＇s data rate up to 3Gbit/s,is designed, assembled, and measured. A top-emitting 850nm vertical cavity surface emitting laser（VCSEL） array is adopted as the light source,and the VCSEL chip is directly wire bonded to a 12 channel driver IC. The outputs of the VCSEL array are directly butt coupled into a 12 channel fiber array. Small form factor pluggable （SFP） packaging technology is used in the module to support hot pluggable in application. The performance results of the module are demonstrated. At an operating current of 8mA, an eye diagram at 3Gbit/s is achieved with an optical output of more than 1mW.

Phase-stabilized RF transmission system based on LLRF controller and optical delay line

Radio frequency(RF)transmission systems with high-precision phase stability are required by the next generation of particle colliders and light sources.An RF transmission system was designed to meet this requirement.In this system,RF signal generated at the sending end is modulated onto a continuous wave(CW)optical carrier,transmitted through an optical fiber,and demodulated at the receiving end.The phase drift is detected by a digital phase monitor with femtosecond-level accuracy and compensated by a motorized optical fiber delay line(ODL).The measurement results show that the long-term phase drifts can be stabilized to within 100 fs(pk-pk),500 fs(pk-pk),and 1.8 ps(pk-pk)in a 400-meter-long optical fiber over 1 h,24 h,and 10 days,respectively.

Study on the Technology of Supplying Water Safely by Long-Distance Pipeline

The extensively built long-distance water transmission pipelines have become the main water sources for urban areas. To ensure the reliability and safety of the water supply, from the viewpoint of overall management, it would be necessary to establish a system of information management for the pipeline. The monitoring, calculating and analyzing functions of the system serve to give controlling instructions and safe operating rules to the automatic equipment and technician, making sure the resistance coefficient distribution along the pipeline is reasonable; the hydraulic state transition is smooth when operating conditions change or water supply accidents occur, avoiding the damage of water hammer. This paper covered the composition structures of the information management system of long-distance water transmission pipelines and the functions of the subsystems, and finally elaborated on the approaches and steps of building a mathematics model for the analysis of dynamic hydraulic status.