Optoelectronic oscillator

Abstract

The invention relates to an optoelectronic oscillator (1) having at least one electro-optical conversion unit (LD1) and an opto-electronic conversion unit (PD1), wherein the light of the electro-optical conversion unit (LD1) which can be emitted during operation can be modulated, wherein some of the light of the electro-optical conversion unit (LD1) irradiates onto the opto-electronic conversion unit (PD1) during operation, wherein the modulated electrical signal generated by the irradiated light of the electro-optical conversion unit (LD1) in the opto-electronic conversion unit (PD1) is used to control the modulation of the light which can be emitted from the electro-optical conversion unit (LD1) during operation, wherein an oscillation is formed during operation.

Description

[0001] Optoelectronic oscillator

[0002] The invention relates to an optoelectronic oscillator.

[0003] background

[0004] With increasing digitalization, the need for systems with optical clock distribution or optical signal distribution is also growing, which require a certain average signal power with a certain optical modulation at different spatial points.

[0005] For this purpose, lasers with subsequent electro-optical modulators and possibly optical splitters are mainly used.

[0006] While it is possible to build such systems with discrete components, this is very expensive and not energy-efficient due to the biasing of the modulators at any operating point. Furthermore, external electrical signal generators are required to drive the modulators.

[0007] For example, from the article "System characteristics of directly modulated and externally modulated RF fiber-optic links" by Stephens, WE and Joseph, TR, published in J. Lightwave Technol., vol. 5, pages 380, DOI: 10.1109 / JLT.1987.1075509, a system is known in which the optical signal is generated by modulating the current of a laser diode. The modulation signal itself was realized using an external source. Finally, the electrical control signal was added to the DC current of the laser using a BIAS-T.

[0008] From the article "Novel technique for generation of optical SSB with carrier using a single MZM to overcome fiber chromatic dispersion" by authors GH Smith, D. Novak; and Z. Ahmed, published in International Topical Meeting on Microwave Photonics. MWP '96 Technical Digest. Satellite Workshop (Cat. NO.96TH8153), 1996, pages 5-8 suppl., doi: 10.1109 / MWP.1996.660352, a system is known in which the optical signal is generated using an electro-optical modulator. An electrical signal is then used to modulate the optical signal.

[0009] A similar arrangement is also known from the article "Suppression of second-order harmonic distortion in ROF links utilizing dual-output MZM and balanced detection" by the authors Y. Cui, K. Xu, Y. Dai and J. Lin, published in 2012 IEEE International Topical Meeting on Microwave Photonics, 2012, pages 103-106, doi: 10.1109 / MWP.2012.6474066, where a pseudo-differential optical output is provided.

[0010] From the article "Optoelectronic oscillator for photonic systems" by authors XS Yao and L. Maleki, published in IEEE Journal of Quantum Electronics, vol. 32, no. 7, pages 1141-1149, July 1996, doi: 10.1109 / 3.517013, a system is known in which an optical signal is modulated by an optical modulator. The optical output signal of the modulator is converted into an electrical signal by a photodiode, amplified, and filtered before becoming the control signal of the modulator.

[0011] However, the previous solutions are essentially characterized by the fact that optical signals are generated by means of external signal generators, whose output signal is used to modulate the optical signal.

[0012] It should also be noted that multiple identical optical signals can only be realized using an optical power splitter or multiple optical sources and modulators.

[0013] In the case of an optical power splitter, the power in each branch decreases by a factor of 1 / N, where N is the divider ratio. To achieve a sufficiently high optical power in each branch, either the optical sources would have to deliver arbitrarily high power, which is not feasible, or any number of optical sources would have to be phase- and frequency-locked in the optical domain.

[0014] Frequency locking would be possible, for example, with thermal elements, which increase the system's power dissipation. Phase locking would require additional optical phase shifters. Overall, the additional hardware significantly increases the complexity, cost, and size of the system.

[0015] It should also be noted that electro-optical modulators only function up to a maximum optical input power and are destroyed beyond this. Therefore, such a solution would be only partially feasible.

[0016] In the case of multiple optical sources and modulators, additional electrical amplifiers may be necessary to amplify the signal from the electrical signal generator. This, in turn, increases the system's power dissipation and increases the signal's phase noise. Furthermore, optical modulators, due to their nonlinear characteristics, generate additional harmonics of the desired distributed signal. Furthermore, discrete optical modulators are very expensive, whereas integrated optical modulators have high attenuation and high assembly costs. Therefore, this solution would also be impractical.

[0017] Furthermore, optical modulators are biased at the 3dB point (quadrature point) for maximum linearity.

[0018] However, this results in a loss of 3dB of signal power, which is then not available in the optical path.

[0019] Task

[0020] Based on the disadvantages listed above, it is an object of the invention to provide an improvement that allows higher performance to be provided at moderate manufacturing costs.

[0021] Brief description of the invention

[0022] The object is achieved by an electro-optical mixer with electrical output according to claim 1. Further advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures.

[0023] Embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

[0024] Fig. 1 is a first abstracted block diagram of an embodiment of the invention,

[0025] Fig. 2 is a second abstracted block diagram of a further embodiment of the invention,

[0026] Fig. 3-5 each show a schematic representation of an embodiment of the invention based on a cross-coupled LC oscillator,

[0027] Fig. 6-8 each show a schematic representation of an embodiment of the invention based on a Colpitt oscillator,

[0028] Fig. 9 is a schematic representation of an embodiment of the invention based on a Clapp oscillator,

[0029] Fig. 10 is a schematic representation of an embodiment of the invention based on ring oscillator,

[0030] Fig. 11 is a schematic representation of an implementation of an inverter gate, and Fig. 12 is a schematic representation of an embodiment of the invention based on a YIG oscillator.

[0031] Detailed description of the invention with reference to the drawings

[0032] The invention will be described in more detail below with reference to the figures. It should be noted that various aspects are described, each of which can be used individually or in combination. This means that any aspect can be used with different embodiments of the invention unless explicitly presented as a mere alternative.

[0033] Furthermore, for the sake of simplicity, reference will generally only be made to one entity in the following. Unless explicitly stated, the invention may also comprise several of the entities in question. Therefore, the use of the words "a," "an," and "another" is to be understood merely as an indication that at least one entity is used in a simple embodiment.

[0034] Where procedures are described below, the individual steps of a procedure can be arranged and / or combined in any order, unless the context explicitly indicates otherwise. Furthermore, the procedures can be combined with one another, unless expressly indicated otherwise.

[0035] Numerical values ​​are generally not to be understood as exact values, but also include a tolerance of + / - 1% to + / - 10%.

[0036] References to standards or specifications or norms are to be understood as references to standards or specifications or norms that are / were in effect at the time of the application and / or, if priority is claimed, also at the time of the priority application. However, this does not imply a general exclusion of applicability to subsequent or replacing standards or specifications or norms.

[0037] Figures 1-12 illustrate various embodiments of the invention. Common to these is that the invention depicts an optoelectronic oscillator 1. This optoelectronic oscillator 1 comprises at least one electro-optical conversion unit LD1 and one optoelectronic conversion unit PD1.

[0038] When the optoelectronic oscillator 1 is in operation, the emittable light of the electro-optical conversion unit LD1 is modulated. A portion of the light from the electro-optical conversion unit LD1 is radiated onto the optoelectronic conversion unit PD1 during operation. The modulated electrical signal generated by the radiated light from the electro-optical conversion unit LD1 in the optoelectronic conversion unit PD1 is used to control the modulation of the light emitted by the electro-optical conversion unit LD1 during operation, resulting in an oscillation.

[0039] Fig. 1 shows a first exemplary block diagram of the invention. The system with the (electrical) transfer function of the control loop H(joo) and / or the (optical) transfer function of the control loop G(jw) controls a control signal in a signal path of one or any number of optical sources and / or optical modulators LD1...LDN. These optical sources and / or optical modulators LD1...LDN can be interconnected in any desired manner, e.g., they can be connected (partially) in series or (partially) in parallel, or a combination of the two circuit topologies can be interconnected.

[0040] The optical output signal UJ of the optical sources and / or optical modulators LD1...LDN is then the output signal of the system.

[0041] The control loop can be closed using an electrical and / or optical signal.

[0042] With a suitable choice of the (electrical) transfer function H(joo) and / or the (optical) transfer function of the control loop, the oscillation condition is fulfilled and the optical signal oscillates.

[0043] In general, a modulatable optical source can be designed as either a directly modulatable source or an indirectly modulatable source. An indirectly modulatable optical source can, for example, comprise a source that emits light continuously compared to the modulation and is modulated by a modulator M. For example, a continuous-wave laser diode with a modulator can be used.

[0044] Fig. 2 shows a second block diagram of the invention. The system with the transfer function of the open (electrical) control loop H(joj) and / or the (optical) control loop G(jco) controls a control signal from one or any number of optical sources and / or optical modulators LD1...LDN. These optical sources and / or optical modulators LD1...LDN can be interconnected in any desired manner, e.g., they can be connected (partially) in series or (partially) in parallel, or a combination of the two circuit topologies can be connected together.

[0045] The optical output signal of one of the sources and / or optical modulators LD1...LDN, or a fraction of the output signal of the optical sources and / or optical modulators (lc)tp, is then optically connected via an optical channel to a photodiode PD1, which is connected to the input of the control loop. This closes the control loop.

[0046] With a suitable choice of the (electrical) transfer function H(joj) and ) and / or the (optical) transfer function G(jw) (and a sufficient coupling of the optical system), the oscillation condition is fulfilled and the optical signal oscillates.

[0047] Figures 3 to 11 show possible implementations of the invention. It should be noted that these implementations are only examples and are used to illustrate functional diagrams, but are not limited to these implementations.

[0048] For example, the electro-optical conversion can be realized with a modulated source and / or optical modulators LD1...LDN.

[0049] In particular, the (directly) modulated source LD1...LDN can be implemented as an LED or a laser. Likewise, a continuously emitting light source with an optical modulator can be used for a modulated source LD1...LDN.

[0050] In particular, embodiments can provide that the light emitted during operation of an optical source can be controlled in a modulated manner by a controllable modulator M.

[0051] In embodiments of the invention, the modulator M can be implemented as an intensity modulator, as a Mach Zehnder modulator or as a ring modulator.

[0052] According to further embodiments, an electro-optical conversion PD1, PD2 can be realized with an optical antenna and / or a photodiode and / or a phototransistor.

[0053] In embodiments of the invention, the optoelectronic oscillator 1 can be implemented as a cross-coupled LC oscillator, as shown by way of example in Figures 3-5. Figures 3-5 differ essentially only in that the optical sources and / or optical modulators LD1, LD2 are arranged differently. Instead of one optical source and / or one optical modulator LD1, any number of sources LD1...LDN can be used. In particular, in Figure 5, the optical source in the emitter branch can also be used for feedback.

[0054] In alternative embodiments of the invention, the optoelectronic oscillator 1 can be implemented as a Colpitt oscillator, as shown by way of example in Figures 6-8. In a further alternative embodiment of the invention, the optoelectronic oscillator 1 can also be implemented as a Clapp oscillator, as shown by way of example in Figure 9.

[0055] In yet another alternative embodiment of the invention, the optoelectronic oscillator 1 can also be implemented as a ring oscillator, as shown by way of example in Figure 10. In particular, the ring oscillator can have an inverter gate as shown in Figure 12.

[0056] According to a further alternative embodiment of the invention, the optoelectronic oscillator 1 can also be designed as a YIG oscillator, as shown by way of example in Figure 11.

[0057] Without limiting the generality, the invention enables an arrangement of several electro-optical conversion units LD2... LDN which have an optoelectronic oscillator 1 according to the invention, wherein the several electro-optical conversion units LD2... LDN are controlled by the optoelectronic oscillator 1.

[0058] In particular, at least some of the plurality of electro-optical conversion units can be connected in parallel or in series.

[0059] Without limiting the generality, it is also possible to construct the optoelectronic oscillator 1 of the invention not only fully integrated, but also partially integrated, ie at least partially with discrete components, as well as only discretely.

[0060] In embodiments of the invention, it is also provided that the output frequency or the frequency of the envelope of the optoelectronic oscillator 1 or the frequency of the optical output signal of the optoelectronic oscillator 1 is detunable.

[0061] According to further embodiments, the detunability of the optoelectronic oscillator (1) can be realized by means of electrical components and / or optical components.

[0062] In particular, the tunability of the optoelectronic oscillator 1 can be realized by means of an adjustable resonator and / or a phase shifter and / or capacitors and / or coils and / or delay lines and / or frequency shifters and / or optical modulators M. In particular, in the case of tunability by means of optical modulators, the optical modulator can be realized as an intensity modulator or as a Mach Zehnder modulator or as a ring modulator.

[0063] Insofar as a resonator is shown in the figures, this can in particular also be designed as a tunable resonator.

[0064] Furthermore, it can also be provided that the optical signal MJ is also split so that it can be guided to different locations (with low intensity).

[0065] The invention makes it possible to generate an optical output signal without external signal sources. Within the scope of the invention, an optical return channel without an optical modulator is used for this purpose. The optical source and / or the optical modulator LD1...LDN are modulated directly by the system.

[0066] Due to the direct modulation of the optical sources, no additional cost-intensive components such as modulators are necessary.

[0067] Furthermore, any number of optical sources and / or optical modulators LD1...LDN can be cascaded or connected in parallel, providing any number of paths with full laser power. Should the optical sources and / or optical modulators LD1...LDN deliver too much optical amplitude and / or extinction ratio, the output signal from each optical source can be further divided into a corresponding number of paths.

[0068] In the case of a differential oscillator structure, the optical signals are also pseudo-differential.

[0069] Due to its simple and robust design, the invention is also suitable for environments with high environmental requirements. In particular, the invention can be used in radar systems, e.g., in vehicles.

Claims

Patent claims 1. Optoelectronic oscillator (1) comprising at least one electro-optical conversion unit (LD1) and one optoelectronic conversion unit (PD1), wherein the light emitted by the electro-optical conversion unit (LD1) during operation is modulatable, wherein a portion of the light from the electro-optical conversion unit (LD1) radiates onto the optoelectronic conversion unit (PD1) during operation, wherein the modulated electrical signal generated in the optoelectronic conversion unit (PD1) by the radiated light from the electro-optical conversion unit (LD1) is used to control the modulation of the light emitted by the electro-optical conversion unit (LD1) during operation, wherein an oscillation is formed during operation.

2. Optoelectronic oscillator (1) according to claim 1, characterized in that the electro-optical conversion is realized with a modulated source (LD1...LDN) and / or with an optical modulator (M).

3. Optoelectronic oscillator (1) according to claim 1 and 2, characterized in that the directly modulated source (LD1...LDN) is realized as an LED and / or laser.

4. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the electro-optical conversion unit (LD1) has a modulator (M) and the modulator (M) is realized as an intensity modulator.

5. Optoelectronic oscillator (1) according to claim 4, characterized in that the modulator (M) is realized as a Mach Zehnder modulator or as a ring modulator.

6. Optoelectronic oscillator (1) according to claim 1, characterized in that the electro-optical conversion (LD1...LDN) is realized with an optical antenna.

7. Optoelectronic oscillator (1) according to claim 1, characterized in that the optoelectronic conversion (PD1) is realized with a photodiode or with a phototransistor or with an optical antenna.

8. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the optoelectronic oscillator (1) is realized as a cross-coupled LC oscillator or as a Colpitt oscillator or as a Clapp oscillator or as a ring oscillator or is designed as a YIG oscillator.

9. Optoelectronic oscillator (1) according to claim 5, characterized in that the ring oscillator has an inverter gate.

10. An arrangement of a plurality of electro-optical conversion units (LD2... LDN), further comprising an optoelectronic oscillator (1) according to one of the preceding claims, wherein the plurality of electro-optical conversion units (LD2... LDN) are controlled by the optoelectronic oscillator (1).

11. Arrangement according to claim 10, characterized in that at least some of the plurality of electro-optical conversion units are connected in parallel.

12. Arrangement according to claim 10, characterized in that at least some of the plurality of electro-optical conversion units are connected in series.

13. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the optoelectronic oscillator (1) is constructed with discrete components.

14. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the optoelectronic oscillator (1) is partially integrated or fully integrated.

15. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the output frequency of the optoelectronic oscillator (1) or the frequency of the envelope of the optoelectronic oscillator (1) or the frequency of the optical output signal of the optoelectronic oscillator (1) is detunable.

16. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the tunability of the optoelectronic oscillator (1) is realized by means of electrical components or by means of optical components.

17. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the detunability of the optoelectronic oscillator (1) is realized by means of an adjustable resonator or by means of phase shifters or by means of capacitors or by means of coils or by means of a delay line or by means of frequency shifters.

18. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the tunability of the optoelectronic oscillator (1) is realized by means of an optical modulator (M).

19. Optoelectronic oscillator (1) according to one of the preceding claims, characterized in that the modulator (M) of the optoelectronic oscillator (1) is realized as an intensity modulator or as a Mach Zehnder or as a ring modulator.

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