Telefonaktiebolaget Lm Ericsson (publ)

Acreo Ab and System 3r International Ab

Anders G Djupsjobacka

Lars Helge Thylen

Lars Egnell

Olof G Sahlen

The invention provides a method and system for measuring the length of a reflective resonator, by analyzing an electromagnetic spectrum emitted therefrom. The emitted spectrum is used for estimating a first cavity length. This estimation is thereafter improved, by first computing at least one interference number for the spectrum, adjust this value to e.g. an integer or half-integer depending on the configuration of the resonator, and thereafter re-calculating the length of the resonator using the adjusted value of the interference number. The above is an efficient way of improving the accuracy in the determination of a physical property of a resonator.

Resonator length measurement

In transmission of optical signals in a dispersive medium, the signals are transmitted simultaneously in two modes in an optical fiber (15), which are orthogonal to each other, one of the signals being a non-chirped amplitude modulated signal modulated by an amplitude modulator (3), and the other signal is a phase modulated signal modulated by a phase modulator (5). The received signal is formed by the sum of the amplitude modulated contributions of the two signals. In an optical fiber system, two orthogonal modes of polarization in the same fiber can be chosen. In this manner it will be possible to transmit high bit rates and primarily over long distances.

Compensation of dispersion

The present invention relates to a device for velocity matching between optical and electrical signals in a waveguide structure comprising first waveguiding means for optical signals and second waveguiding means for electrical signals. The cross-section of the waveguide structure varies dielectrically in the direction of the propagation.

Device for velocity matching between electrical and optical signals in a

The present invention relates to a device and a method respectively for dispersion compensation in a fibre optic transmission system in which an optic signal is fed to the device. The device comprises an optic separating device for spectral optic splitting of the optic input signal into two branches in an upper and lower modulation sideband, a delay device for selective delay of the spectral bands in relation to one another, and a combining device for combining the sidebands.

Device and method for dispersion compensation in a fiber optic

A system and a method for dispersion compensation in fiber optic high speed systems, the dispersion compensation being carried out in the transmitter. The system comprises a modulating device for modulating an information-carrying electric signal, an equalizing device for equalizing the signal modulated in the modulation device, and an electro-optic translating device for translating the signal equalized in the equalizing device into an optical signal substantially without loss of information and with substantially maintained phase and amplitude properties.

System and method for dispersion compensation in fibre optic high speed

A method of linearizing a modulator (1) having two parallel-coupled sub-modulators (2, 3). The complete transmission function of the modulator includes parameters which relate to power division (A, 1-A) of a non-modulated carrier wave (P.sub.in) and a relationship (B) between the activation degree of the sub-modulators (2, 3). The transmission function is simplified and series-expanded with two higher-order terms, each having a respective coefficient. An expression for intermodulation distortion is calculated with the aid of the series-expansion and with control signals (V1, V2) having two or three frequencies. The signs of the coefficients are determined so that the terms having these coefficients will mutually counteract their respective distortion contributions, and limited search regions for the parameters (A, B) are calculated with the aid of the sign-determined coefficients. In accordance with secondary conditions for high electrooptic efficiency and pronounced modulation depth, the distortion level of the modulator is calculated with the aid of the complete transmission function in the search regions.

Method of linearizing the transmission function of modulator

A modulator arrangement comprises two Mach-Zehnder modulators, a main modulator (2) and a compensation modulator (3) having non-linear transmission functions. The modulators (2, 3) are controlled by a modulating control signal (V), via electrodes (16, 17). A carrier wave (S1) from a laser (7) is power divided (a, 1-a) into part-waves in a power divider (5) between the modulators (2, 3). The modulated part-waves (S2, S3) are superimposed at an output (14) to produce a resultant modulated wave (S4). A linearized transmission function between the control voltage (V) and the power of the resultant modulated wave (S4) has a radius of curvature whose length is maximized within a control voltage range, so as to minimize intermodulation distortion. The mean slope of the transmission function is maximized within this range. At a common control voltage (V) for the modulators (2, 3), the modulator arrangement has an optimal transmission function at a length ratio b=.sqroot.3:1 between the modulators (2, 3), and a power ratio between the part-waves of .sqroot.3:9. The main modulator (2) is the shortest and modulates the strongest part-wave.

Method of linearizing a transmission function of a modulator

The invention relates to an electrode arrangement for optoelectronic devices. A wafer (11) of electro-optical material has on its upper surface a first elongate electrode (12) and a second U-shaped electrode (13). The electrodes (12, 13) are mutually spaced (d.sub.1) apart in an interaction region (L.sub.1) with light wave guides (14). The first electrode (22) has a connecting conductor (15) for an incoming microwave signal (S.sub.1) with the aid of which a light wave (P) is to be modulated. The connecting conductor (15) divides the first electrode (12) into a standing wave guide (17) and a travelling wave guide (18), which is connected via resistor (R.sub.1) to the second electrode (13). The incoming microwave signal (S.sub.1) is divided up in the reflection point (16) into a standing wave (S.sub.2) and a travelling wave (S.sub.3), which co-act in the modulation of the light wave (P). The electrode arrangement results in a modulator of bandpass character, which requires relatively low voltage in the incoming microwave signal (S.sub.1). The modulator center frequency can be selected by selecting the length (L.sub.1) of the standing wave guide (17).

Electrode arrangement for optoelectronic devices

An optoelectronic directional coupler (1) has in a coupling area two parallel, coupled lightwave conductors (6a and 6b) with a length (L) as well as electrodes (5a and 5b). Each of the coupled lightwave conductors has one end connected to its individual output (7a and 7b) of the directional coupler (1). At their other ends the coupled lightwave conductors are each connected to its extra individual lightwave conductor (8a and 8b), the conductors (8a and 8b) being connected to the directional coupler input (9) via a fork branch. An incoming lightwave (P) is divided into two partial lightwaves (P1 and P2) by the extra wave conductors (8a and 8b). The partial lightwaves are in phase with each other and have the same effect in relation to each other at the inputs to the coupled lightwave conductors (6a and 6b). The partial lightwaves can be switched to either of the outputs (7aand 7b) with the aid of a control signal (S) connected between the electrodes (5a and 5b). The directional coupler has the advantage that the control signal (S) is a pure alternating voltage.

Optoelectronic directional coupler for a bias-free control signal

An Optoelectric connection device (3a) for coupling transmission (28) and reception units (4) to a line (2) for optical information transmission. The device includes a plate (11) of optoelectric material having two directional couplers (12,13) connectable to the line (2) and a modulating directional coupler (14). A signal at the input (18,18a) for the line is cross-coupled in the first coupler (13) to the reception unit (4). A lightwave from the source (28) is modulated in the modulator (14) to form an output signal, which is cross coupled in the second coupler (12) to the output (23,23a) for the line. If the directional couplers (12,13a) are disabled, a signal at the input (18,18a) passes via the couplers directly to the output (23,23a). The connection device has a reserve input (19,19a) and a reserve output (24,24a) which are utilized for fitting the connection device into the line (2) without interrupting signal transmission on the line (2). The device (3a) has negligible cross talk between the input (18,18a) and output (23,23a).

Optoelectric connection device

An optoelectronic modulator for generating an optical signal in which a wafer (10) of optoelectronic material has two parallel light wave conductors (13a,13b) and three planar electrodes (14a,14b,14c). The latter are arranged so that two electrodes adjacent each other define by their long sides an elongate intermediate space with at most three sections, which are transversely displaced in relation to each other. One long side of one of the sections is situated approximately in the line of extension of the other long side in an adjacent section and the lightwave conductors (13a,13b) are situated in the extension lines. The lightwave conductors are modulated in counter-phase in two adjacently situated sections by a modulating alternating voltage (U) which is connected to the electrodes. The ratio between the length (L.sub.1) of the longest section and the length (L) of the electrodes is in the range of 0.70 to 0.95. By the electrode configuration, the modulator is given high upper boundary frequency and good pulse response.

Optoelectronic modulator

A method of increasing the available bandwidth of a high speed modulator in which an optical signal is modulated by a microwave signal (v) along an interaction distance (L). After passing half the interaction distance (L/2) the modulating signal is pole reversed by a positive (+E) and a negative (-E) bias voltage being connected to two different sections of the interaction distance. An apparatus according the method in an optical directional coupler modulator is described.

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Solna, Sweden

Anders G Djupsjobacka