490 results about "Multi core fiber" patented technology

The invention provides a wavelength division multiplexing-fused multi-core optical fiber temperature detection method and system. Wherein the broadband light source is divided into multiple wavelength channels through wavelength division multiplexing, and a wavelength-fiber core mapping relation is established, so that each fiber core of the multi-core optical fiber transmits a single-wavelength optical signal. An optical fiber is integrated to the surface of an object according to a three-dimensional path, each fiber core covers a plurality of sensing sub-areas, the wavelength drift amount caused by temperature is extracted by detecting the attenuation characteristic of an optical signal at a bending position, the wavelength drift amount is converted into a temperature value in combination with a calibration curve, and a temperature gradient model bound with the fiber core position is constructed. And further performing spatial solution by using fiber core spacing, wavelength mapping and transmission time delay parameters, establishing a corresponding relationship between the coordinates of the sensing sub-regions and the temperature, and finally reconstructing three-dimensional temperature field distribution. According to the technical scheme provided by the invention, high-resolution dynamic reconstruction and gradient analysis of a three-dimensional temperature field on a complex surface are realized through wavelength-space two-dimensional decoupling.

The invention discloses a multi-mode optical signal transmission method and device, electronic equipment and a storage medium, and relates to the technical field of computers.The transmitted data stream is divided into a control signal and a data signal, the control signal is a visible light wave band, the data signal is an infrared wave band, and the control signal and the data signal are combined to a single multi-core optical fiber through a combiner; the optical network controller allocates subcarrier resources as required according to the change of network flow in a spectrum dynamic allocation mode to perform data transmission, so that the subcarrier resource allocation adapted to the change of network flow improves the dynamic adaptability, and the allocation of the subcarrier resources as required improves the equipment cooperation efficiency, and in the data transmission process, the data transmission efficiency is improved. Clock synchronization and signal encryption are realized through a quantum key distribution mode, and the security is improved.

The invention provides a high and low temperature alternating environment temperature and pressure mixed signal decoupling method and system based on a multi-core optical fiber. According to the method, temperature and pressure mixed signals are synchronously acquired through phase difference data of a plurality of fiber cores, and multi-channel mixed sensing signals are generated; performing mechanical stress suppression on the multi-core optical fiber by using a thermal expansion adaptive packaging structure to form an anti-deformation optical fiber assembly; carrying out adaptive time slot distribution on the mixed sensing signal based on a time division multiplexing time sequence to generate a synchronous calibration signal; spectral features of the synchronous calibration signals are separated through the spectral analysis technology, scanning parameters are dynamically adjusted in combination with the temperature change rate and the deformation quantity, and temperature and pressure feature data are extracted; and performing decoupling operation on the feature data through the coupling model, and dynamically correcting the model parameter weight based on the deformation quantity feedback data to obtain a temperature parameter and a pressure parameter. According to the invention, the accuracy of synchronous decoupling measurement of temperature and pressure in a high-low temperature alternating environment is realized.

The invention discloses a multi-core optical fiber multichannel demodulation system for three-dimensional displacement measurement of a mechanical oscillator, which comprises a light source module, a multi-core optical fiber sensing probe, a photoelectric detection module and a signal processing module. A mapping model between multi-channel optical signals and displacement is established, decoupling and high-precision measurement of three-dimensional displacement are realized through a matrix demodulation algorithm, the system takes a multi-core optical fiber as an integrated probe structure, free space optical path alignment is not needed, an optical path is stable, and packaging is simple and convenient; compared with a traditional single-core optical fiber displacement sensing scheme, displacement components of the mechanical oscillator in the three orthogonal directions can be obtained at the same time, and the method has the advantages of being high in measurement precision, high in anti-interference capacity, good in real-time performance, compact in system structure and the like and can be widely applied to the fields of mechanical oscillator displacement measurement, structure health monitoring, precision manufacturing, micro-nano operation positioning and the like.

The invention discloses a parallel imaging OCT (Optical Coherence Tomography) system based on a metasurface area array, which relates to the technical field of medical instruments, is small in size and can realize intraocular single-shot area array imaging and a three-dimensional position depth perception function by using metasurface and optical coherence tomography imaging information in a sample tissue with a limited size. According to the technical scheme, a light beam emitted by a laser is divided into two paths through a beam splitter, and the two paths enter a sample arm module and a reference arm module respectively; the sample arm module is a probe and comprises a multi-core optical fiber and a first metasurface; the reference arm module comprises a collimator, a motor and a right-angle reflector; the probe enters a sample tissue, a light beam is focused on the sample tissue and then is backscattered, the backscattered light beam reversely passes through the first metasurface, the multi-core optical fiber, the beam splitter, the second metasurface, the third lens, the grating and the focusing lens and then forms a spectral line beam on the CCD sensor, and the computer reads a signal from the CCD sensor and performs three-dimensional reconstruction imaging on the sample tissue.

A system and method directed to detecting placement of a medical device within a patient body, the system including a medical device including a multi-core optical fiber having a plurality of core fibers. Each of the plurality of core fibers can include a plurality of sensors each configured to reflect a light signal having an altered characteristic due to strain experienced by the multi-core optical fiber. The system can further include logic configured to determine a 3D shape of the medical device in accordance with the strain of the optical fiber. The logic can be configured to define a reference plane for the 3D shape and render an image of the 3D shape on a display of the system in accordance with the reference plane.

A system, apparatus and method directed to detecting malposition of a medical device within a vessel of a patient, such as an Azygos vein. The medical device can include a multi-core optical fiber including a plurality of core fibers, where each of the plurality of core fibers includes a plurality of sensors is configured to reflect a light signal based on received incident light, and change a characteristic of the reflected light signal for use in determining a physical state of the multi-core optical fiber. The system can include a console having non-transitory computer-readable medium storing logic that, when executed, causes operations of providing a broadband incident light signal to the multi-core optical fiber, receiving reflected light signals, processing the reflected light signals, and determining whether the medical device has entered the Azygos vein of the patient based on the reflected light signals.

The invention relates to the technical field of optical fiber performance analysis, in particular to a multi-core fiber grating multi-parameter decoupling method based on improved CNN-LSTM. According to the method, a multi-core fiber grating temperature, vibration and three-dimensional deformation detection system is built, center wavelength data under the action of different physical loads are collected, and the center wavelength data are matched with corresponding real physical quantities to build a supervised learning data set. After abnormal value elimination, filtering noise reduction and normalization processing are carried out on collected signals, stratified sampling and data enhancement are adopted to construct a training set and a test set. An improved CNN-LSTM model is established, multi-parameter nonlinear mapping and feature focusing are realized in combination with convolutional feature extraction, time sequence modeling and an attention mechanism, training is performed by taking RMSE as a loss function and an Adam optimizer, and an early stop mechanism is set to prevent overfitting. After training is completed, wavelength data to be measured are input into the model, and temperature, vibration and three-dimensional deformation results after decoupling can be output.

A system, apparatus and method directed to placing a medical device into a body of a patient, including performing operations of providing a broadband incident light signal to a plurality of core fibers of a multi-core optical fiber, receiving reflected light signals of different wavelengths, and processing the reflected light signals associated with the plurality of core fibers to determine (i) a physical state of the multi-core optical fiber relating to the medical device including the multi-core optical fiber, and (ii) an orientation of the multi-core optical fiber relative to a reference frame of the body. Additional operations include generating a display illustrating the physical state of the multi-core optical fiber based at least on the orientation determined during processing of the reflected light. Typically, the display is a two-dimensional representation of the multi-core optical fiber in accordance with the determined orientation.

An MCF includes a plurality of cores each extending in a direction along a central axis and a cladding covering each of the plurality of cores. The cladding includes a low refractive index barrier. The low refractive index barrier includes an alkali metal element. A relative refractive index of the low refractive index barrier is lower than an average value of a relative refractive indices of the cladding overall. The core interval is set such that a total sum of the power coupling coefficients between a specific core among the plurality of cores and each of all remaining cores is 2.3×10−4 / km or less.

The utility model relates to the technical field of optical fiber conduction, and discloses a receiver assembly which is used for butting a connector with a multi-core optical fiber, butting sections of a plurality of single-core optical fibers are combined and arranged in an insertion core through hole formed in a receiver insertion core part, and are aligned and fixed with the receiver insertion core part used for butting a connector insertion core; the receiver insertion core piece is fixedly arranged in the adjusting piece, an adjusting through hole is formed in the receiver shell, the adjusting through hole and the insertion core through hole are coaxial, the adjusting piece is arranged in the adjusting through hole, so that the receiver insertion core piece is arranged in the adjusting through hole in a penetrating mode, and the adjusting piece and the receiver shell can selectively, coaxially and relatively rotate; the receiver assembly is assembled in advance and then is in butt joint with the connector. The adjusting piece can adjust the fiber cores of the multiple single-core optical fibers to be aligned with the fiber cores of the multi-core optical fibers one by one. And after the receiver assembly is adjusted to a correct angle, the relative positions of the adjusting piece and the receiver shell are fixed, so that the receiver assembly is simpler and more compact in structure, and the space of butt joint action can be saved.

The invention discloses a non-destructive and high-precision testing and calibrating device and method for internal geometric parameters of a multi-core optical fiber. The device comprises a two-dimensional arc groove testing mold, a first rotating clamp, a second rotating clamp, a fan-in and fan-out device, an optical switch, an optical frequency domain reflectometer and data collecting and processing equipment. By embedding the to-be-measured multi-core optical fiber into the groove with the known curvature and combining the distributed strain demodulation technology, the distributed strain distribution in the bending state is directly measured, and the distributed strain distribution in the bending state is directly measured through a mathematical model of the bending-torsion composite action and a cosine function fitting algorithm without cutting or damaging the optical fiber structure. And synchronously calculating the torsion period, the core spacing and the core included angle. The method overcomes the defects that a traditional microscope method depends on end face preparation and destructive detection, realizes on-line measurement of all-fiber length, can adapt to multi-core fibers with different core numbers and cladding structures, and can be expanded to high-precision industrial scenes such as fiber-optic gyroscope calibration, flexible conduit morphology monitoring, submarine optical cable process optimization and the like.

The present invention relates to the field of communication and sensing, and specifically to a communication and sensing integrated device based on a seven-core optical fiber interferometer and an application method therefor. The application method comprises: a first beam splitter splitting, into reference light and signal light, a light source emitted by a narrow linewidth laser; performing modulation by means of a first coherent optical transmitter and a second coherent optical transmitter; amplifying the light by means of a first amplifier and a second amplifier, and then enabling the light to pass through a multi-core optical fiber from a fan-in end, and to output from a fan-out end; performing beam splitting by means of a second beam splitter and a third beam splitter, and performing demodulation by means of a first coherent receiver and a second coherent receiver; and finally, a phase-locked loop performing interference elimination on preliminarily-demodulated reference light and preliminarily-demodulated signal light to obtain finally-demodulated reference light and finally-demodulated signal light. The present invention uses a phase-locked loop to further eliminate disturbance noise of reference light and signal light. Therefore, noise interference is eliminated in continuous low-frequency detection, thereby improving the communication and sensing effect.

The invention discloses a distributed optical fiber two-dimensional vector sensing system and method, the system uses an acousto-optic modulator group and an optical circulator group to ask a plurality of fiber cores of a multi-core optical fiber in parallel, heterodyne coherent detection uses local oscillator light to improve the signal-to-noise ratio, and through the relation between the fiber core position difference and the direction angle of a two-dimensional sound wave in the aspect of algorithm, the two-dimensional sound wave direction angle is obtained. According to the space division multiplexing distributed optical fiber acoustic sensing system, a two-dimensional vector signal is accurately restored, the measurement vector angle range of the space division multiplexing distributed optical fiber acoustic sensing system for two-dimensional sound waves is 0-360 degrees, the vector sensing range is larger than 50 km and far exceeds that of an existing system, and the detection capacity of the distributed optical fiber acoustic sensing system is greatly improved.

The invention belongs to the related technical field of sensors, and provides a multi-parameter integrated acquisition optical fiber sensor and a monitoring system thereof in order to solve the problem that high-precision monitoring of a static signal and a dynamic signal is difficult to consider by an existing sensor at the same time, a sensing cavity is sequentially divided into a static signal sensing area and a dynamic signal sensing area in the axial direction; the static signal sensing area adopts a multi-core fiber, fiber gratings are respectively engraved on the multi-core fiber, and the wavelength demodulation of the static signal is realized through the central wavelength drift distance of the fiber gratings; the dynamic signal sensing area is provided with a dynamic signal sensing unit, the dynamic signal sensing unit comprises F-P air microcavities formed between the dynamic signal sensing unit and the end faces of all fiber cores of the multi-core optical fiber, and intensity demodulation of dynamic signals is achieved through cavity length changes of the F-P air microcavities. According to the invention, a wavelength modulation and intensity modulation parallel composite demodulation mechanism is adopted, and decoupling acquisition of static strain, temperature and dynamic vibration is realized in a single sensor.

The invention provides a multi-core optical fiber, a parallel optical transmission optical module and an optical interconnection system, which can solve the problem of high operation and maintenance cost caused by coexistence of PSM and WDM optical modules and non-uniform optical module interface and optical fiber wiring in the prior art, the multi-core optical fiber comprises a multi-core optical fiber, the size of a central fiber core is the same as that of a single-mode optical fiber, and the optical interconnection system comprises a single-mode optical fiber and a single-mode optical fiber. The wavelength division multiplexing module is used for transmitting wavelength division multiplexing optical signals; the plurality of peripheral fiber cores are arranged around the central fiber core and are used for transmitting multiple paths of parallel optical signals; an optical interface of the parallel optical transmission optical module is connected with a peripheral fiber core of the multi-core optical fiber, and the parallel optical transmission optical module is used for transmitting multiple paths of parallel optical signals through the peripheral fiber core; the wavelength division multiplexing optical module is provided with a single-channel optical interface, and the single-channel optical interface is connected with the central fiber core of the multi-core optical fiber and used for transmitting wavelength division multiplexing optical signals through the central fiber core.

The invention provides a multi-point distributed temperature detection method and system based on a multi-core optical fiber structure. Wherein grating array etching processing is carried out on at least three fiber cores to form a specific reflection wavelength interval; when an external light source is incident, the fiber core grating structures reflect optical signals with corresponding wavelengths to generate reflected optical signals with different wavebands; the method comprises the following steps: dividing a reflected light signal channel through a wavelength branching device, generating independent channel signals of each fiber core, and simultaneously carrying out time sequence separation on multi-grating signals in the same fiber core to obtain reflected signals in discrete time sequence distribution; combining the independent channel signal with the discrete reflection signal, performing interference comparison with the fixed wavelength reference optical signal, generating a phase difference interference signal reflecting wavelength shift, and analyzing the wavelength shift to obtain temperature-related wavelength shift data; and through analysis and stress error elimination under deformation constraint, outputting a temperature detection result. According to the technical scheme provided by the invention, the accuracy of distributed temperature detection is improved.

The invention provides a multi-core optical fiber strain and temperature decoupling method and system for grating demodulation, electronic equipment and a storage medium, and relates to the technical field of optical fiber sensing, and the method comprises the steps: obtaining the lowest wavelength data of the spectrum of fiber cores at two sides of an air layer of a multi-core optical fiber, and recording the position data of a light spot formed by the secondary dispersion of a diffraction grating at the same time. The diffraction grating is used for secondary light splitting of the composite light, independent spectrum data are generated, and two-core coupling is blocked through an air layer. A double-task analysis network is constructed, strain wavelength offset is obtained through strain branches, and temperature wavelength correction is obtained through temperature branches. Network weight is adjusted in combination with related data to generate a strain demodulation value of temperature decoupling, the strain demodulation value is converted into a standardized signal to be transmitted to a monitoring system, an axial strain dynamic distribution diagram is reconstructed, a temperature compensation curve is synchronously displayed, multi-core optical fiber strain and temperature accurate decoupling can be achieved, strain information can be dynamically obtained, and the distribution and compensation state can be synchronously displayed.

The present invention relates to the technical field of optical fiber sensing. Disclosed are a multi-core grating sensor and a manufacturing method therefor, and a permafrost monitoring method. The multi-core grating sensor comprises a multi-core optical fiber grating, a strain gauge structure, and a demodulator, and the multi-core optical fiber grating comprises four uniformly and symmetrically distributed single-mode optical fibers, a cladding layer wrapping the four single-mode optical fibers, and a coating layer located between the single-mode optical fibers and the cladding layer; the strain gauge structure is attached to the outside of the multi-core optical fiber grating by means of glue bonding; and the demodulator is used for monitoring the dynamic change of the wavelength of the multi-core optical fiber grating, the demodulator comprises a broadband light source and a spectrum analyzer, an incident end of the multi-core optical fiber grating is connected to the broadband light source by means of the single-mode optical fibers, and an exit end thereof is connected to the spectrum analyzer by means of the single-mode optical fibers. Also disclosed in the present invention is a permafrost monitoring method. By means of comprehensive analysis and demodulation of fiber core wavelength variation amounts of a plurality of single-mode optical fibers on a single multi-core optical fiber grating, simultaneous measurement of multiple parameters is achieved, and the permafrost monitoring accuracy is improved.

The invention discloses a multi-core optical fiber amplifier with a large core-to-cladding ratio and a gain method. The multi-core optical fiber amplifier is characterized by comprising a multi-core optical fiber formed by a plurality of independent rare earth-doped fiber cores and a cladding structure located on the outer side of the multi-core optical fiber, the cladding structure is internally provided with at least one layer of low-refractive-index isolation region which is used for remarkably compressing the effective cladding area of pumping propagation and improving the capturing efficiency of the whole pumping energy, and the ratio of the total cross sectional area of the multi-core optical fiber to the effective cladding area is not less than 0.1. The low-refractive-index isolating layer is embedded in a conventional cladding structure, so that a pump light propagation area can be effectively compressed on an optical path, the relative proportion of the fiber core in the cross section is increased, the proportion (CCAR is larger than or equal to 0.1) of the total area of the fiber core to the cladding area is remarkably increased, and therefore the pump capture efficiency is improved.

The invention discloses an anti-fading noise phase type optical frequency domain reflection three-dimensional deformation measurement device and method, and the method comprises the steps: transmitting a detection signal, and dividing the detection signal into a measurement path and a reference path; performing mode multiplexing on the measurement path signal through a photon lantern to generate mode-multiplexed multi-path multi-mode detection light, and enabling the multi-path multi-mode detection light to enter different fiber cores of a few-mode multi-core optical fiber respectively; performing optical domain frequency mixing on the reflected light of the three-dimensional deformation information of different fiber cores of the few-mode multi-core optical fiber and the reference path signal to obtain beat frequency signals of different optical modes of each fiber core; and carrying out phase averaging on the beat frequency signals of different optical modes in each fiber core to obtain strain information of different fiber cores, and reconstructing three-dimensional deformation of the few-mode multi-core fiber by combining a Freen-Serret frame. According to the invention, effective measurement of the spatial three-dimensional shape is realized while the coherent fading noise is compensated, and the method has the characteristics of high sensitivity and high spatial resolution, and is suitable for three-dimensional shape sensing in a complex environment.

The invention provides a multi-core optical fiber tunable structure and a preparation method thereof, and relates to the technical field of photonic devices. The multi-core optical fiber tunable structure comprises a fan-in and fan-out module, a section of multi-core optical fiber and at least two Fabry-Perot interference cavities; the physical cavity lengths of the at least two Fabry-Perot interference cavities are different from each other; the multi-core optical fiber is provided with a first end face and a second end face, and the multi-core optical fiber comprises at least two fiber cores; the at least two Fabry-Perot interference cavities and the at least two fiber cores are arranged in a one-to-one correspondence manner; each Fabry-Perot interference cavity comprises a first reflecting surface and a second reflecting surface; and the first reflecting surface is an end surface of the fiber core corresponding to the Fabry-Perot interference cavity at the second end surface of the multi-core optical fiber. On the basis, the problems that an existing discrete integrated multi-channel tuning structure is complex in structure, high in insertion loss, low in reliability and high in cost and packaging difficulty are solved.

1. The name of the design product: multi-core fiber ribbonizer. 2. The use of the design product: used in optical fiber laser, submarine cable, optical migration sensor, petrochemical optical fiber, medical optical fiber, optical module ribbonizer. 3. The design points of the design product: in shape. 4. The picture or photo that best shows the design points: perspective view 1.

A distributed reconfigurable switching node for a multi-core optical fiber is disclosed. A method and system for transmission of optical signals. The system includes one or more first switching optical devices configured to switch transmission of one or more optical signals from one or more first fiber cores to one or more second fiber cores. It includes one or more second switching optical devices configured to pass transmission of one or more optical signals from one or more first fiber cores to one or more third fiber cores.

A multi-core fiber includes a cladding, cores extending in an extending direction inside the cladding, a marker inside the cladding, and an end surface inclined in an inclined direction that is not orthogonal to the extending direction. The cores at the end surface are line-symmetrically arranged with respect to a virtual axis orthogonal to the inclination direction. The virtual axis virtually divides the end surface into a first area and a second area. The cores include a first core disposed farthest from the virtual axis in the first area and a second core disposed farthest from the virtual axis in the second area. A center of the marker at the end surface is disposed in an area between a straight line, passing through the first core, parallel to the virtual axis and a straight line, passing through the second core, parallel to the virtual axis.

The invention discloses a belt conveyor safety online monitoring method and device, a medium and a product, and relates to the field of belt conveyor safety monitoring, and the method comprises the steps: collecting a multi-vibration-source signal and a temperature signal of a belt conveyor through a vibration reduction and sensitization acoustic vibration optical cable device; the vibration reduction and sensitization acoustic vibration optical cable device is of a multi-core optical fiber spiral winding structure, and a gradient vibration reduction layer is integrated on the outer layer. Sequentially carrying out wavelet packet decomposition, blind source separation and deep learning optimization on the multi-vibration-source signal, and determining a single-vibration-source signal corresponding to each part; performing time synchronization on the single vibration source signal and the corresponding temperature signal by adopting a dual-optical fiber redundant link and an optical fiber gyroscope; and performing multi-source data fusion diagnosis by adopting a D-S evidence theory according to the synchronized single vibration source signal and the corresponding temperature signal in combination with a sound signal, and generating a fault early warning signal. The distributed optical fiber monitoring accuracy and stability of the belt conveyor can be improved.

Intensity control units 40A and 40B acquire the intensity of backscattered light when inputting signal light of two or more modes for each core in a multicore optical fiber 10, which has two or more cores and in which two or more modes propagate to each of the cores, so that the transmission direction of light differs between adjacent cores, and output a control signal for reducing the input optical power of a high-order mode other than a basic mode of the signal light by a predetermined amount so as to reduce the influence of the high-order mode on the basic mode.

The invention relates to the technical field of optical fiber connectors, and provides a multi-core optical fiber connector and a processing method thereof, and the multi-core optical fiber connector comprises a multi-core tail handle optical fiber, a reference base, a PIN base and at least two PINs. The multi-core tail handle optical fiber comprises a connector insertion core; the reference base is positioned and connected to one side of the multi-core tail handle optical fiber, and the reference base is provided with at least two first coupling alignment reference holes; the PIN is arranged on the PIN base and connected with the PIN base, the PIN base is arranged on the other side of the multi-core tail handle optical fiber, the PIN penetrates through the first coupling alignment reference hole, and the free end of the PIN is used for being in positioning connection with a second coupling alignment reference hole in an external multi-core optical fiber interface assembly. And the connector insertion core is coupled and aligned with the interface insertion core of the multi-core optical fiber interface assembly. According to the invention, high-precision alignment connection is realized, stable transmission is further realized, and the connection problem of the jumper wire of the multi-core optical fiber connector is solved by matching with the multi-core optical fiber interface assembly.

The invention discloses a flexible splitter, which comprises a splitter main body and an internal space, the internal space can accommodate a multi-core optical fiber, the splitter main body further comprises a deformation part, and the deformation part can be subjected to elastic deformation or plastic bending deformation as required. The flexible splitter is provided with the deformation part which can be bent and deformed, and the deformation part enables the splitter to be elastically or plastically bent and deformed, so that the splitter is allowed to have certain flexibility. In addition, because the optical cable also has flexibility, the optical cable provided with the flexible splitter can still keep good bending deformation performance, when the optical cable provided with the flexible splitter is arranged in a narrow and complex environment, the bending state of the deformation area of the splitter can be adjusted at any time according to the use requirements of the environment, and the flexibility of the optical cable is improved. The difficulty of optical cable wiring is reduced, and troubles caused by a hard splitter in the wiring process are avoided.

A multicore optical fiber may include a common cladding comprising a radius R4 defining a glass portion of the optical fiber and having a cladding relative refractive index Δ4. At least two waveguides may extend through the common cladding. Each waveguide may include a core region, an inner cladding region, and a depressed cladding region. Each core region may include a maximum relative refractive index Δ1max. Each inner cladding region may include a relative refractive index Δ2. Each depressed cladding region may include a minimum relative refractive index Δ3min and a trench volume from 20-45%µm2 such that Δ1max>Δ2>Δ3min, and Δ4>Δ3min. A cable cutoff wavelength of each waveguide is ≤1150 nm. The co-propagating and counter-propagating inter-waveguide cross talk between each waveguide and a nearest waveguide is <-35 dB at 1310 nm and <-20 dB at 1550 nm for application lengths of 20 m. A mode field diameter of each waveguide is 8.2-9.0 µm at 1310 nm.