Crosstalk Values Research Articles

Crosstalk investigation of laser-diode pairs

The crosstalk between the lasers of different laser-diode pairs has been investigated experimentally in the frequency domain. The mutual crosstalk of two lasers diodes monolithically integrated on a single transmitter chip and separated by 100 mu m was measured to be about -50 dB up to a modulation frequency of 100 MHz. At higher frequencies, it rises linearly with the frequency to -40 dB at 1 GHz. Measurements and calculations indicate that the origin of this crosstalk is the leakage current in the chip and inductive coupling of the bond wires. With these crosstalk values, digital data transmission at high bit rates is possible without significantly reducing the receiver sensitivity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Controllable integrated-optic polarization splitter-combiner

We propose and demonstrate an individually controllable TE–TM polarization splitter–combiner. Using these controllable characteristics, we can tune the cross-talk values of the fabricated devices to their optimum values. The measured cross-talk values for the TE and TM polarizations of our device are lower than −20 dB at operational voltages of less than 20 V.

A small-size polarization splitter based on a planar optical phased array

A device is proposed in which the dispersive properties of an array of bent optical waveguides are utilized for splitting the two polarizations present in the input waveguide. An experimental device for operation at a 633- mu m wavelength, with dimensions of 0.6*2.5 mm/sup 2/, was designed and fabricated using conventional (high-quality) optical lithography. Insertion losses as low as 0.5 dB and far-end crosstalk values of 17-21 dB have been achieved. >

Low-loss planar optical polarisation splitter with small dimensions

A novel planar polarisation splitter with the smallest dimensions thus far reported (0.6 × 2.5 mm2) is presented. The component, which is based on an optical phased array, was designed and fabricated using conventional (high-quality) optical lithography. Insertion losses as low as 0.5 dB and crosstalk values of 17–21 dB have been achieved.

Integrated-optic wavelength multiplexers on lithium niobate based on two-mode interference

The principle of the wavelength-dependent two-mode interference (TMI) in guided wave devices is utilized to build up integrated-optic dual-channel wavelength-division multi-/demultiplexers (WDM) for single-mode systems. The device characteristics are analyzed by analytical and numerical methods where special emphasis is given to the wavelength dependence of the channel spacing. These devices are fabricated by titanium indiffusion into X-cut and Y- and Z-propagating LiNbO/sub 3/, where the Z-propagating configuration is preferred for polarization independent operation. In the wavelength range between 1.3 and 1.6 mu m, insertion losses (fiber-waveguide-fiber) below 3 dB, channel spacings of 30-40 nm, and far-end crosstalk values of 26-40 dB are achieved. The measured low temperature sensitivity of the wavelength shift of 5.6*10/sup -2/ nm/ degrees C and the possibility of electrooptic tuning at a rate of 2.5 nm/V allow the realization of high performance devices at reduced fabrication tolerances. >

Flat passband birefringent wavelength-division multiplexers

Birefringent filter synthesis techniques are demonstrated to achieve very flat channel passbands for wavelength-division multiplexers. The crystal thickness and birefringence can be used to scale a given design to very small channel separations, limited primarily by the spectra of the lasers and their drift. Experimental results are reported, with typical optical crosstalk values of –19 dB.

Tunable birefringent wavelength-division multiplexer/demultiplexer

A tunable wavelength-division multiplexer/demultiplexer, based on a polarisation-insensitive birefringent optical filter design, is described. The two channels of the device can each be tuned, with the channel separation adjustable over a wide range. Experiments with 6 to 30 nm laser channel separations have yielded optical crosstalk values of less than −20 dB.

Optical waveguide 2 × 2 matrix switch using dielectric chip motion

Input and output light angles in a total internal reflection optical waveguide switch, in which a guided light beam is switched by dielectric chip contact with a low-index channel built in a waveguide film, are studied to construct a matrix switch. Output angle depends on channel width, chip contact width, chip position, and input angle. In a single switch experiment, the output angle is larger than the total reflection critical angle for the channel due to narrow chip contact width. By utilizing this property, a nonblocking 2 x 2 matrix switch, driven by PZT bimorphs, is fabricated. Insertion losses of 2.9-6.0 dB, cross talk values of 10.8-28.1 dB, and switching time of 6 msec are obtained for the TE(0) mode at 0.633-microm wavelength.

Measurement of side-write, -erase, and -read behavior of conventional narrow track disk heads

Narrow track recording heads suffer from wavelength dependent side fringing effects. During writing these manifest themselves in track widening and erasing of neighboring tracks, and during reading in side fringing response and crosstalk. Side fringing fields have been analyzed theoretically but experimental verification of this phenomena is scarce. Measured values of actual track width, erasing width and crosstalk are reported. The measurements have been performed with specially manufactured disk heads with widths ranging from 10-50 μm. One set of heads was constructed similar to the 3330-II heads. Another set was constructed such that they resemble as closely as possible the shape of the theoretical head that is used as a model. Some heads were locally narrowed by laser machining. Actual track width was measured as a function of write current amplitude at low recording density (no pulse crowding) and as a function of wavelength at optimum write current amplitude. The measured track widening agrees with theory and can be as high as 5 μm at either side of the head at optimum write current and low pulse density. Track widening decreases with decreasing wavelength. The distance from the head side at which the head still effectively erases can be as high as 15μm. In a disk drive this will be the factor that limits the track density. Inter track read crosstalk is determined by measuring the displacement curve (i.e., the curve representing the read signal versus position as the head is shifted across its own track at different wavelengths). The curves agree with theory except for the presence of "side lobes."

Measurement of side-write, -erase and -read behaviour of conventional narrow track disk heads

Narrow track recording heads suffer from wavelength dependent fringing effects. During writing these manifest themselves in track widening and erasing of neighboring tracks, and during reading in fringing response and crosstalk. Side fringing fields have been analyzed theoretically but experimental verification of this phenomena is scarce. Measured values of actual track width, erasing width and crosstalk are reported. The measurements have been performed with specially manufactured disk heads with widths ranging from 10-50 μm. One set of heads was constructed similar to the 3330-II heads. Another set was constructed such that they resemble as closely as possible the shape of the theoretical head that is used as a model. Some heads were locally narrowed by laser machining. Actual track width was measured as a function of write current amplitude at low recording density (no pulse crowding) and as a function of wavelength at optimum write current amplitude. The measured track widening agrees with theory and can be as high as 5 μm at either of the head at optimum write current and low pulse density. Track widening decreases with decreasing wavelength. The distance from the head at which the head still effectively erases can be as high as 15μm. In a disk drive this will be the factor that limits the track density. Inter track read crosstalk is determined by measuring the displacement curve (i.e., the curve representing the read signal versus position as the head is shifted across its own track at different wavelengths). The curves agree with theory except for the presence of side lobes.

Experimental Evaluation of an Optical Time Division Demultiplexer for Twenty-four Channels

Experimental techniques for optical demultiplexing by use of sinusoidal polarization switches were evaluated. For this purpose the terminals of a twenty-four-channel optical PCM system were simulated by two channels separated in time by1/24th the pulse period. The complete twenty-four PCM channels would have an information rate of 6.7 Gbit/sec. The measured values of cross talk in the demultiplexer were -13 dB and -9 dB for the two channels used in the simulated system. The major contributions to the cross talk were (1) intrinsic cross talk due to the use of a sine wave rather than a square wave for polarization switching (-19.6 dB and -13.1 dB); (2) light leakage in the demultiplexer crystals due to rf heating that gives rise to a nonuniform birefringence (-19 dB, both channels); and (3) misadjustment of the demultiplexer.

Crosstalk in t.d.m.–p.a.m. switching systems due to capacitive coupling in the highway-interconnecting network

Expressions are derived for the inter-highway crosstalk due to capacitive coupling in the highway-interconnecting network as functions of the parameters of the transmission path and the time shift between the switching control pulses. An analogous relation can be derived for the inter-highway crosstalk due to the mutual inductance between neighbouring highways; however, this kind of coupling can easily be reduced to negligible values. Measured crosstalk values are in close agreement with the theoretical results.

Crosstalk in Coaxial Cables-Analysis Based on Short-Circuited and Open Tertiaries

The problem considered herein is that of estimating, from measurements on short lengths of coaxial cable, the crosstalk to be expected in long lengths of the same cable. The method developed, which is particularly applicable to cases in which the effect of tertiary circuits on the crosstalk is large, is based on measurements of crosstalk in a short length, with the tertiaries first short-circuited and then open. The application of this method to the cable described in the companion paper by Messrs. Booth and Odarenko gave crosstalk values in good agreement with their experimental results.