TECHNICAL FIELD

Embodiments of the disclosure relate to an optoelectrical chip, a measurement system including an optoelectrical chip, as well as a method for evaluating a reflection spectrum of a fiber Bragg grating that uses an optoelectrical chip.

In measurement-technological applications using light, it is in many cases required for a reflection spectrum or a transmission spectrum of the light used for measurement to be evaluated. For example, light is influenced by optical elements in its spectral properties, e.g. by optical gratings such as fiber Bragg gratings, and the spectral properties of the light that had been subjected to such an influence are evaluated. The spectral properties of the light comprise, for example, a wavelength-dependent intensity minimum or maximum.

STATE OF THE ART

Optoelectrical chips are known, on or in which optical elements and electric or electronic elements are arranged and interconnected in the form of a mixed optical and electrical system, typically on or in a common wafer for the respective optical and electric/electronic elements.

FIG. 4shows an example of a conventional optoelectrical chip101. Into the chip101, an optical waveguide110is inserted, the inserted end of which forms a light inlet opening111for entering light150. The entering light150, for example, is light which had been changed in its spectral properties on its propagation path from a light source (not shown) to the light inlet opening111, wherein some or all of the further elements of the chip101serve to measure spectral properties of interest or spectral property changes. Typically, a wavelength-related maximum of the intensity of the entering light150was influenced or shifted by a fiber Bragg grating (not shown) which is formed in the optical waveguide110.

The light150entered into the chip101is divided into a first light fraction151and a second light fraction152by a beam splitter120. The first light fraction151subsequently passes an optical filter130in its transmission, which filter performs a wavelength-dependent filtering of the light. The filtered light153exiting the optical filter130hits a filter photodiode140where it generates an electric measurement signal depending on its intensity.

The second light fraction152hits a reference photodiode160where it generates an electric reference signal depending on its intensity. The second light fraction152is unfiltered. The value of the measurement signal is divided by the value of the reference signal, for example, in an evaluation circuit (not shown). Via a calibrating model of the optical filter130, the wavelength of the fiber Bragg grating within the optical waveguide110may be deduced from the thus obtained quotient.

The optoelectrical chip101is of a relatively complex structure inter alia due to the beam splitter120, and the sensitivity is low due to the beam splitter120. A solution is desirable, in which the complexity of an optoelectrical chip101is reduced and/or the sensitivity is improved.

SUMMARY

Embodiments of the present disclosure provide an optoelectrical chip having the features of claim1. Further, embodiments of the present disclosure propose a measurement system having the features of claim8which uses an optoelectrical chip disclosed herein. Furthermore, embodiments of the present disclosure provide a method having the features of claim9for evaluating a reflection spectrum of a fiber Bragg grating, in which method an optoelectrical chip disclosed herein is used.

According to an embodiment, an optoelectrical chip comprising the following elements is proposed: a light inlet opening; a wavelength-sensitive optical filter; a first photoelectric element for measuring a first light intensity, particularly a first photodiode; the first photoelectric element being arranged such that light entering into the optoelectrical chip via the light inlet opening, which is transmitted by the filter, hits the first photoelectric element; and a second photoelectric element for measuring a second light intensity, particularly a second photodiode, the second photoelectric element being arranged such that light entering into the optoelectrical chip via the light inlet opening, which is reflected at the filter, hits the second photoelectric element.

A measurement system disclosed herein features an optoelectrical chip described herein, and an optical waveguide coupled to the light inlet opening, the optical waveguide comprising at least one fiber Bragg grating.

A method for evaluating a reflection spectrum of a fiber Bragg grating, the fiber Bragg grating being provided in an optical waveguide, and an end of the optical waveguide being inserted in the light inlet opening of an optoelectrical chip described herein, comprises: measuring a transmission intensity of the light having entered via the light inlet opening and having passed the optical filter, by means of the first photoelectric element; measuring a reflection intensity of the light having entered via the light inlet opening and having been reflected at the optical filter, by means of the second photoelectric element; dividing the transmission intensity by the reflection intensity to obtain a ratio value; and relating the ratio value to a model of the optical filter to obtain a value associated with the reflection spectrum.

The filter element, i.e. the wavelength-sensitive optical filter accordingly is utilized both in transmission and reflection. The light reflected at the filter element is used directly to measure a reference intensity. The filter surface thus functions as a beam splitter.

The light having entered via the light inlet opening and having passed the optical filter, together with the light having entered via the light inlet opening and having been reflected at the optical filter, is subject to energy conservation. The fact that no separate beam splitter or a similar optical element attenuating the light intensity is used, the efficiency of the optoelectrical chip described herein is doubled as compared to a conventional optoelectrical chip.

The saved beam splitter element moreover reduces manufacturing costs, for example, material costs and possible labor costs in manufacturing the chip.

The transmission function regarding wavelength, which is present at the first photoelectric element, is applied to the second photoelectric element in a wavelength-inverse manner. A division of the two intensities measured at the respective photoelectric elements, therefore may result in an improved signal-to-noise ratio.

In embodiments of the optoelectrical chip, the measurement system and/or the method, the optical filter is a wavelength-sensitive transmission filter or an edge filter.

In embodiments of the optoelectrical chip, the measurement system and/or the method, a reflection surface of the optical filter is inclined relative to the propagation direction of the light entering into the optoelectrical chip via the inlet opening, in particular within an angular range from 10° to 80° relative to a perpendicular orientation of the reflection surface with respect to the propagation direction.

An inclination of the reflection surface of the optical filter can enable the second photoelectric element to be arranged in or on the optoelectrical chip in a space-saving manner, for example, adjacent to an inserted optical waveguide.

In embodiments of the optoelectrical chip, the measurement system and/or the method, the light path from the light inlet opening to the filter, the light path from the filter to the first photoelectric element, and the light path from the filter to the second photoelectric element each are free from further optical elements. The intensity of the light whose spectral properties are assessed in the optoelectrical chip, is therefore not subjected to any significant attenuation which occurs, for example, in a separately provided beam splitter. Thus, the sensitivity can be improved.

In embodiments of the optoelectrical chip, the measurement system and/or the method, the optoelectrical chip further comprises an evaluation circuit. A first measurement signal from the first photoelectric element and a second measurement signal from the second photoelectric element are supplied to the evaluation circuit. The respective values of the measurement signals are associated with the respective measured light intensities. The evaluation circuit is configured to divide the value of the first measurement signal by the value of the second measurement signal in order to obtain a ratio value.

An evaluation circuit integrated with the optoelectrical chip may contribute to a further simplification and/or compaction in an optoelectrical measurement system.

Typically, the evaluation circuit is configured to relate the ratio value to a model of the optical filter so as to obtain a value associated with a spectrum of the light entering via the light inlet opening. The value, for example, indicates a frequency-dependent intensity maximum or an intensity minimum of the light entering via the light inlet opening. The model of the optical filter typically is a model suitable for calibrating purposes of the filter. A calibrating model of the optical filter typically comprises a look-up table. The ratio value e.g. allows for a wavelength or wavelength shift of a fiber Bragg grating formed in the optical waveguide to be deduced.

