Abstract:
A coupled quantum well Mach-Zehnder modulator that employs a push-pull structure to reduce the modulation voltage. The Mach-Zehnder modulator includes a first arm having a first PIN semiconductor device and a second arm having a second PIN semiconductor device. The intrinsic layers of the PIN devices include a coupled quantum well structure to provide an opposite index of refraction change for different DC bias voltages. An RF signal used to modulate the light beam is applied to the two arms in phase and causes the index of refraction in the intrinsic layers of the two PIN devices to change in opposite directions so that a push-pull type drive is achieved without requiring 180° out-of-phase RF drive signal.
Abstract:
Bei diesem Modulator (MO) und dem dazugehörigen Verfahren für eine optische Modulation werden in beiden Armen (BR1,BR2) eines Interferometers, deren optische Weglängen sich um eine halbe Lichtwellenlänge unterscheiden, jeweils ein Elektroabsorptionsmodulator vorgesehen (MO1,MO2), die mit Gegentaktspannungen angesteuert werden. Auf diese Weise lassen sich wahlweise eine chirparme Amplitudenumtastung und eine chirparme Phasenumtastung realisieren bei äußerst kleinen notwendigen Steuerspannungen.
Abstract:
An optic intensity modulator includes a substrate (10) of an optic material that is conductive to light and acoustic waves and has both the electro-optic and piezoelectric properties. The optical modulator generally consists of a Mach-Zender interferometer comprising a pair of associated elongated light waveguides (11, 12) formed in the substrate, with the waveguides extending substantially coextensively with one another, and being separated from one another by a transverse distance that gradually varies along the courses of the waveguides. Different phase shifts are induced by imposing variable electric fields onto each of the waveguides by means of electrodes (21, 22, 23). Because of the varying spacing between the waveguides along their courses, the tendency of the acoustic waves that are generated during the operation of the modulator due to the piezoelectric effect to resonate between the waveguides at certain frequencies, is eliminated thus reducing the corresponding noise distortion.
Abstract:
Un modulateur d'intensité optique comprend un substrat (10) d'un matériau optique conducteur de la lumière et des ondes acoustiques, et possède à la fois des propriétés électro-optiques et piézoélectriques. Le modulateur optique se compose généralement d'un interféromètre Mach-Zender comprenant une paire de guides d'ondes lumineux, allongés, combinés (11, 12) formés dans le substrat, ces guides d'ondes s'étendant pratiquement sur une même étendue les uns par rapport aux autres, et se trouvant séparés les uns des autres d'une distance transversale qui varie graduellement le long de leurs déplacements. Des décalages de phase différents sont induits en imposant des champs électriques variables sur chacun des guides d'ondes au moyen d'électrodes (21, 22, 23). Du fait de l'écartement variable des guides d'ondes le long de leurs déplacements, la tendance des ondes acoustiques, générées lors du fonctionnement du modulateur par l'effet piézoélectrique, à résonner entre les guides d'ondes à certaines fréquences, est éliminée, réduisaant ainsi la distorsion de bruit correspondante.
Abstract:
An apparatus includes an optical splitter, an optical intensity combiner, first and second Mach-Zehnder interferometers, and first and second drive electrodes. The first Mach-Zehnder interferometer connects a first optical output of the optical intensity splitter to a first optical input of the optical intensity combiner. The second Mach- Zehnder interferometer connects a second optical output of the optical intensity splitter to a second optical input of the optical intensity combiner. The first drive electrode is located between and connected to a pair of semiconductor junctions along first internal optical arms of the Mach-Zehnder interferometers. The second drive electrode is located between and connected to a pair of semiconductor junctions along second internal optical arms of the Mach-Zehnder interferometers.
Abstract:
A driving circuit and Mach-Zehnder EAM optical modulator exhibiting negligible chirp that generates a PSK signal when driven by a single drive signal. Two such Mach-Zehnder EAM optical modulators and drive circuits may be configured in parallel, thereby generating DQPSK signals with only two drive signals, one for each individual Mach-Zehnder EAM modulator.
Abstract:
There is provided an optical duobinary (ODB) transmission system, including a duobinary precoder receiving data signals and converting the signals into first and second different digital signals each composed of two level voltages; a duobinary encoder fed by the precoder for converting the digital signals into three level analog signals, and a close loop control circuit for maintaining equal drive voltages for driving a Mach Zehnder Modulator (MZM). A method of encoding NRZ data for optical duobinary (ODB) transmission is also provided.
Abstract:
A method for controlling an optoelectronic component that includes two waveguides (3 and 4). The refractive index of the first waveguide (3) is changed periodically with a first control signal (1), the amplitude of which is changed between a first amplitude level (I) and higher second amplitude level (II). The refractive index of the second waveguide (4) is changed periodically with a second control signal (2), the amplitude of which is changed between the aforementioned first amplitude level (I) and a lower third amplitude level (III). When the control signals are on their common first amplitude level (I), the refractive indices of the waveguides are equal and the phase difference between them is zero. When the first control signal is on the second amplitude level (II) and the second control signal on the third amplitude level (III), the refractive indices of the waveguides are unequal so that their mutual phase difference has a predetermined target value. For accelerating a phase-difference change both control signals are adjusted during both the rise and the fall time periods simultaneously so that their combined effect leads to a very fast phase difference change, which settles already before the refractive indices of the waveguides are settled.
Abstract:
An optical waveguide that guides an incident light is formed on an a substrate having an electro−optical effect. A first buffer layer is formed so as to cover the top surface of the substrate. A conductive film is formed above the first buffer layer. A center electrode and a groung electrode are formed to apply voltage to the optical waveguide so as to induce an electric field therein. A second buffer layer is formed between the conductive film and at least one of the center electrode and the ground electrode. The conductive film is so formed as to exist at least a part of and below the ground electrode. Light guided along the optical waveguide is modulated by having the phase thereof changed by voltage applied to the optical waveguide. Accordingly, an optical modulation device is provided that has an excellent electric characteristics by effectively restricting heat drift.
Abstract:
An electro-optic push-pull modulator requiring reduced high switching voltages through combinations of device structure and operation, causing linear and quadratic electro-optic effects to add. Such combinations of device structure and operation include combinations of crystal axis orientation, waveguide structure, electrode structure, electric field biasing, operating wavelengths, and optical polarizations. By inducing linear and quadratic electro-optic effects to add, significant refractive index changes can be realized with lower switching voltages, V pi . Furthermore, significant reduction in switching voltage for push-pull modulators can also be realized through combinations of device structure and operation effectively inducing solely the quadratic electro-optic effect.