CN106444215A - Optical Analog-to-Digital Converter with Configurable Frequency Response - Google Patents

Abstract

An optical analog-to-digital conversion device with configurable frequency response, which sequentially includes: optical sampling clock generation with controllable pulse shape, repetition frequency multiplication, electro-optic modulation, multi-channelization, photoelectric conversion, electrical filtering, electrical analog-to-digital conversion, and digital processing unit and the clock synchronization and alignment module. The invention simultaneously realizes analog processing and digitization of broadband input microwave signals, greatly reduces system complexity, and simultaneously avoids the problems of large insertion loss and signal distortion caused by separate filtering and sampling. The equivalent frequency response of the system can be flexibly configured by adjusting the time domain profile of the optical sampling clock.

Description

Optical Analog-to-Digital Converter with Configurable Frequency Response

technical field

The invention relates to optical analog-to-digital conversion, in particular to an optical analog-to-digital conversion device with configurable frequency response.

Background technique

Due to the limitation of "electronic bottleneck", electronic technology has been difficult to meet the increasingly higher frequency and bandwidth signal processing requirements in the fields of ultra-wideband communication, radar, high-end instruments and scientific research. Photon technology has the advantages of ultra-broadband, ultra-high speed, and high precision, and can effectively overcome the shortcomings of electronic technology. High-frequency broadband signal processing based on photonic technology is currently the focus of attention.

Analog filtering can achieve the purpose of signal frequency selection, phase shift and delay, etc., and is one of the basic analog signal processing technologies. Due to the influence of "electronic bottleneck" in electrical filtering, the performance such as operating frequency is limited. Microwave photonic filters use photonics technology to filter microwave signals, which have the advantages of large bandwidth and low loss, and have great advantages in processing high-frequency signals. At present, a variety of microwave photonic filter schemes have been proposed. There are two traditional methods: the first method is the structure of electric differential, which was realized as early as 1995, but this method is adjustable and adjustable. The reconfiguration is poor, and the bandwidth of the electrical device is limited; the second method is to use complex optoelectronic devices to realize the filter with full coefficients, but this method is very expensive. Recently, many novel low-cost structures have been reported to realize microwave photonic filters with negative coefficients. Among them, the method of using polarization state and external modulator is the most attractive (WANG Q, YAO J.Multitap photonic microwave filters with arbitrary positive and negative coefficients using apolarization modulator and an optical polarizer[J].IEEE Photonics Technology Letters,2008,20(2 ):78-80.).

Digitizing analog signals for storage, processing, transmission and display is the development trend of information technology. The analog-to-digital converter is the core device of digitization. Electronic Analog to Digital Converter (EADC: Electronic Analog to Digital Converter) is affected by factors such as clock jitter and comparator ambiguity, the performance is close to the theoretical limit, and further improvement faces great challenges.

Optical analog-to-digital converter (PADC: Photonic Analog to Digital Converter) uses the advantages of photonics such as broadband and high precision to realize high-precision digitization of broadband signals. It has the advantages of high bandwidth and high sampling rate. Efficient way of precision analog-to-digital conversion. At present, a variety of optical analog-to-digital conversion technology solutions have been proposed, including optical-assisted analog-to-digital converters, optical-sampled electrical analog-to-digital converters, electrical sampling and optical-quantized analog-to-digital converters, and all-optical analog-to-digital converters. Among them, the analog-to-digital converter of optical sampling electrification can simultaneously utilize the advantages of high bandwidth, high precision and mature electrification of photonics, and has become one of the focuses of attention. At present, there are mainly two kinds of analog-to-digital converter schemes for optical sampling electrification: based on wavelength division multiplexing (T.R.Clark, J.U.Kang and R.D.Esman, "Performance of a time and wavelength interleaved photonic sampler for analog-digital conversion," IEEEPhoton.Tech .Lett., vol.11, 1168～1169, 1999) and time-division multiplexing technology (A.Yariv and R.G.M.P.Koumans et al., "Time interleaved optical sampling for ultra-highspeed A/D conversion," Electronics Letters, 34(21):2012-2013, 1998).

In many applications, both filtering and analog-to-digital conversion are required. The currently reported microwave photon filtering and optical analog-to-digital conversion schemes can only perform one of the functions of filtering or analog-to-digital conversion, and the two cannot be directly connected in the optical domain to achieve two functions at the same time. If they are connected by photoelectric conversion, not only the system is complicated, but also additional noise will be introduced.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention provides an optical analog-to-digital conversion device with configurable frequency response. The device is based on the time-interleaved optical analog-to-digital conversion structure. Under the condition that the time-domain width of the electrical filter impulse response is greater than the time-domain pulse width of a single sampling optical pulse, the relationship between the shape of the optical sampling pulse and the frequency response of the optical analog-to-digital converter is used. By changing the time-domain shape of the optical sampling pulse, the configuration of the optical analog-to-digital conversion response is realized, thereby simultaneously realizing the filtering and digitization of the input microwave signal.

Technical solution of the present invention is as follows:

An optical analog-to-digital conversion device with configurable frequency response, including an optical sampling clock generation module (1), which is characterized in that the optical sampling clock generation module is composed of an optical pulse sequence generator and a programmable optical pulse shaper, Along the laser output direction of the programmable optical pulse shaper, there are repetition frequency multiplication module, electro-optical modulator, optical demultiplexer, photoelectric conversion module, electrical filter module, electrical analog-to-digital conversion module and digital processing unit in sequence. The first output terminal of the digital processing unit is connected to the control terminal of the programmable optical pulse shaper, the clock synchronization and alignment module contains an adjustable optical delay device, and the first port of the clock synchronization and alignment module It is connected with the connection between the optical pulse sequence generator and the programmable optical pulse shaper of the optical sampling clock generation module, and the second port of the clock synchronization and alignment module is connected to the electrical analog-to-digital conversion Modules are connected, the third port of the clock synchronization and alignment module is connected to the second output terminal of the digital processing unit, the clock synchronization and alignment module receives the control of the digital processing unit to realize the control of the electrical Synchronization and alignment of the sampling clock and the optical sampling pulse sequence, the sampled signal is input from the modulation end of the electro-optical modulator;

The optical sampling clock generating module generates an optical pulse sequence with controllable time-domain shape according to the configuration of the digital processing unit, and inputs it into the electro-optical modulator after the repetition frequency of the optical sampling pulse sequence is multiplied by the repetition frequency multiplication module; The sampling electrical signal performs intensity modulation on the optical pulse sequence, and the output intensity carries the optical pulse sequence of the sampled electrical signal; the optical pulse sequence enters the optical demultiplexer, and decomplexes the high-speed optical sampling pulse sequence carrying the sampled signal It is used as N low-speed signals; each output low-speed signal corresponds to a photoelectric converter of the photoelectric conversion module and an electrical analog filter of the electrical filter module; each output of the photoelectric conversion module and the electrical filter module The conversion module is converted into digital signals; N channels of digital signals are reconstructed by the digital processing unit to obtain sampled electrical signals, and N is an integer greater than 1.

The optical pulse sequence generator generates the optical pulse sequence and sends it to the input end of the programmable optical pulse shaper, under the control of the digital processing unit, the pulse shape of the optical sampling clock is adjusted, and the generated pulse shape meets the design requirements and the intensity is An optical signal that varies periodically over time configures the frequency response of the system.

There are two types of clock synchronization and alignment modules:

The first one includes an adjustable optical delay line, a photoelectric converter and a phase-locked loop circuit, the optical sampling clock sent by the optical pulse sequence generator is input into the adjustable delay line, and is controlled by the digital processing unit Delay time, so that it can be fine-tuned in one cycle, and then input into the phase-locked loop circuit after being converted into an electrical signal by the photoelectric converter, and input the output signal of the phase-locked loop into the electrical analog-to-digital conversion module as an electrical analog-to-digital conversion The sampling clock of the module, so that the electrical analog-to-digital converter always samples at the highest point of the filtered electrical pulse;

The second type includes a high-stable clock source, a laser repetition rate locker, an adjustable delay, and a phase-locked loop circuit. The high-stable clock source provides a clock signal with low phase noise and low jitter, and the clock signal passes through the laser After the repetition rate locker, input the optical pulse sequence generator to adjust the repetition frequency of the pulse sequence it sends out, and lock it on the high stable clock source; the clock signal is input into the adjustable delay device, so The above-mentioned digital processing unit controls the delay time of the adjustable delayer so that it can be fine-tuned in one cycle, and the delayed clock signal is then input into the phase-locked loop circuit to obtain a stable repetition frequency and electrical analog-to-digital conversion The pulse signal with the same sampling rate as the device provides a sampling clock for the electrical analog-to-digital conversion module, so that the electrical analog-to-digital converter always performs sampling at the highest point of the filtered electrical pulse.

The time-domain width of the electrical filter impulse response is greater than the time-domain pulse width of a single sampling light pulse.

The frequency response of the entire system is configured by adjusting the optical sampling clock and the electrical filter, the system equivalent impulse response h _A (t) and the optical sampling clock time domain waveform p (t) and the electrical filter impulse response h _E (t) Satisfies the relationship: h _A (t) = Kp (-t) h _E (t), K is a constant.

The clock synchronization and alignment module is used for synchronizing and aligning the sampling frequency and phase of the electrical analog-to-digital converter. The clock synchronization and alignment module adjusts the sampling clock of the electrical analog-to-digital converter according to the feedback of the digital processing unit, so that it always performs sampling at the highest point of the filtered electrical pulse. In this way, the strength of the recovered signal can be increased, the influence of noise can be effectively reduced, and the influence of sampling time jitter can also be reduced.

Based on the above technical characteristics, the present invention has the following advantages:

The invention can realize analog-to-digital conversion with configurable frequency response, can simultaneously complete photon filtering and digitization of broadband microwave signals, and the frequency response can be configured and adjusted, greatly reducing the complexity of microwave photon processing and improving flexibility. Since the electrical signal before sampling by the electrical analog-to-digital converter has been filtered, it can effectively reduce the requirements on the analog input performance of the electrical analog-to-digital converter, and break through the limitation of the "electronic bottleneck" of the electrical analog-to-digital converter on the system.

Description of drawings

FIG. 1 is a system block diagram of Embodiment 1 of an optical analog-to-digital conversion device with configurable frequency response according to the present invention.

Fig. 2 is the schematic diagram of working process of embodiment 1.

Fig. 3 is a system block diagram of Embodiment 2 of the optical analog-to-digital conversion device with configurable frequency response of the present invention.

detailed description

The present invention will be further described below in conjunction with drawings and embodiments. The examples are carried out on the premise of the technical solutions of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following examples.

Example 1:

The system block diagram of this embodiment is shown in Figure 1, including: an optical sampling clock generation module 1, a repetition frequency multiplication module 2, an electro-optic modulator 3, an optical demultiplexer 4, a photoelectric conversion module 5, an electrical filter module 6, an electrical module A digital conversion module 7, a digital processing unit 8, and a clock synchronization and alignment module 9.

The optical sampling clock generating module 1 includes an optical pulse train generator (for a mode-locked laser) 1-1 and a programmable optical pulse shaper (for a waveshaper, Finisar, 4000s) 1-2. The optical pulse sequence generator 1-1 generates an optical pulse sequence with a repetition frequency f, and sends it to the input terminal of the programmable optical pulse shaper 1-2. Programmable optical pulse shaper 1-2 according to different needs, under the condition that the time-domain width of the impulse response of the electric filter is greater than the time-domain pulse width of a single sampling optical pulse, under the control of the digital processing unit 8, the The pulse shape of the optical sampling clock is adjusted. The optical sampling clock generation module 1 outputs a sampling optical pulse sequence with a repetition frequency f and a controllable pulse shape, as shown in FIG. 2 .

The spectral division and frequency doubling module 2 adopts the method of spectrum division, and utilizes a wave division multiplexer (arrayed waveguide grating AWG: Arrayed Waveguide Grating) 2-1 to divide the original optical pulse into N sub-pulses of different wavelengths , and sent to the corresponding optical delay line 2-2 and optical attenuator (AT: Attenuator) 2-3, and then carry out wavelength division multiplexing through the wavelength division multiplexer 2-4, and the final output is the sampling rate f×N Optical sampling pulse trains with equal delay intervals. The optical sampling pulse sequence is shown in FIG. 2 .

The electro-optic modulator 3 (a Mach-Zehnder electro-optic modulator) modulates the sampled electrical signal on the optical sampling pulse sequence. The output of the electro-optic modulator is an optical sampled pulse train whose intensity carries the sampled electrical signal, as shown in FIG. 2 .

The optical demultiplexer 4 (arrayed waveguide grating) decomposes the high-speed wavelength division multiplexed optical pulse sequence carrying the sampled signal from the electro-optic modulator into N low-speed parallel optical pulse sequences by means of wave division multiplexing, and each The pulse repetition frequency of one channel is reduced to the repetition frequency f of the sampled optical pulse before wavelength division multiplexing, as shown in Figure 2

The photoelectric conversion module 5 and the electrical filtering module 6 include a plurality of channels, and each channel corresponds to an output channel of the optical demultiplexer. There is an optical-to-electrical converter and electrical-to-analog filter on each channel. Photoelectric converters are used to convert optical signals into electrical signals, which are filtered by electrical filters.

The electrical analog-to-digital conversion module 7 is composed of N electrical analog-to-digital converters with a sampling rate f. Each electrical analog-to-digital converter receives one output of the electrical filter module 6 , converts the input signal into a digital signal and outputs it to the digital processing unit 8 according to the clock signal input by the clock synchronization and alignment module 9 .

The digital processing unit 8 receives user instructions to configure the programmable optical pulse shaper 1-2, and reconstructs the digital signal input by the multi-channel electrical analog-to-digital converter into a filtered and processed sampled signal in the digital processing unit. signal, and control the clock synchronization and alignment module 9 according to the processing result to find the optimal result.

The clock synchronization and alignment module 9, as shown in FIG. 1, includes a dimmable delay line 9-1, a photoelectric converter 9-2 and a phase-locked loop circuit 9-3. The optical sampling clock sent by the optical pulse sequence generator 1-1 is input into the adjustable delay line 9-1, and the delay time of the adjustable delay line 9-1 is controlled by the digital processing unit 8, so that it can be fine-tuned in one cycle After being converted into an electrical signal by the photoelectric converter 9-2, it is input into the phase-locked loop circuit 9-3 to obtain a stable pulse signal with the same repetition frequency as the sampling rate of the electrical analog-to-digital converter. The output signal of the phase-locked loop is input into the electrical analog-to-digital conversion module 7 as the sampling clock of the electrical analog-to-digital conversion module, so that it can be sampled near the highest point of the electrical pulse.

Example 2:

The system block diagram of this embodiment is shown in Figure 3, including: an optical sampling clock generation module 1, a repetition frequency multiplication module 2, an electro-optic modulator 3, an optical demultiplexer 4, a photoelectric conversion module 5, an electrical filter module 6, an electrical module A digital conversion module 7, a digital processing unit 8, and a clock synchronization and alignment module 9.

Modules 1-8 in Embodiment 2 are completely the same as those in Embodiment 1 and will not be repeated here.

Described clock synchronization and alignment module 9, as shown in Figure 3, comprises highly stable clock source 9-1, laser repetition rate locker 9-2, adjustable delayer 9-3 and a phase-locked loop circuit 9- 4. The highly stable clock source 9-1 provides a clock signal with low phase noise and low jitter; the clock signal is input to the optical pulse sequence generator 1-1 after passing through the laser repetition rate locker 9-2 The repetition rate of the pulse train it sends out is adjusted to lock it to a high stability clock source. The clock signal is input to the adjustable delayer 9-3, and the delay time is controlled by the back-end digital processing unit 8, so that it can be fine-tuned in one cycle, and the delayed clock signal is then input into the phase-locked loop In circuit 9-4, a stable pulse signal with the same repetition frequency as the sampling rate of the electrical analog-to-digital converter is obtained, and a sampling clock is provided for the electrical analog-to-digital conversion module 7 so that it can sample at the highest point of the electrical pulse.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (5)

1. the configurable optical analog to digital conversion device of a kind of frequency response, including Optical Sampling clock generation module (1) it is characterised in that Described Optical Sampling clock generation module (1) is by optical pulse sequence generator (1-1) and programmable optical pulse reshaper (1-2) structure Become, the laser outbound course along described programmable optical pulse reshaper (1-2) is repetition rate multiplication modules (2), electricity successively Optical modulator (3), optical multiplexer (4), photoelectric conversion module (5), electric filtration module (6), electric analog-to-digital conversion module (7) and Digital processing element (8), described the first output end of digital processing element (8) and described programmable optical pulse reshaper (1-2) control end is connected, and clock is synchronous to contain adjustable light delay with alignment module (9), described clock synchronous with align The optical pulse sequence generator (1-1) of the first port of module (9) and described Optical Sampling clock generation module (1) and programmable Line between optical pulse shaper (1-2) connects, the synchronous second port with alignment module (9) of described clock with described Electric analog-to-digital conversion module (7) is connected, synchronous the 3rd port with alignment module (9) of described clock and described digital processing list Second output end of first (8) is connected, and described clock is synchronous to receive described digital processing element (8) with alignment module (9) Control, realize the synchronization to electric sampling clock and Optical Sampling pulse train and align, be sampled signal from described Electro-optical Modulation The modulated terminal input of device (3)；

Described Optical Sampling clock generation module (1) produces the controlled light of time domain profile according to the configuration of digital processing element (8) Pulse train, inputs electrooptic modulator after the repetition rate of repetition rate multiplication modules (2) multiplication Optical Sampling pulse train (3)；The reception of this electrooptic modulator is sampled electric signal and carries out intensity modulated to light pulse sequence, and output intensity carries and is sampled electricity The light pulse sequence of signal；This light pulse sequence enters described optical multiplexer (4), will carry the high speed being sampled signal Optical Sampling pulse train is demultiplexing as N road low speed signal；Each road low speed signal of output all corresponds to photoelectric conversion module (5) One optical-electrical converter and an electrical analogue wave filter of electric filtration module (6)；Photoelectric conversion module is every with electric filtration module Road output is converted to data signal by electric analog-to-digital conversion module (7) again；N railway digital signal reconstructs through digital processing element to be adopted The electric signal of sample, N is more than 1 integer.

2. the configurable optical analog to digital conversion device of frequency response according to claim 1 is it is characterised in that light pulse sequence Generator produces the input that light pulse sequence sends into programmable optical pulse reshaper, under the control of digital processing element, right The pulse profile of Optical Sampling clock is adjusted, and generation pulse profile meets design requirement and intensity is periodically variable in time Optical signal, the frequency response to system configures.

3. the configurable optical analog to digital conversion device of frequency response according to claim 1 is it is characterised in that described clock Synchronous have two types with alignment module：

The first includes adjustable optical delay line, optical-electrical converter and a phase-locked loop circuit, described optical pulse sequence generator In the Optical Sampling clock input adjustable delay line sending, time delay is controlled by described digital processing element so as at one It is finely adjusted in cycle, is converted to through optical-electrical converter and inputs in phase-locked loop circuit after electric signal again, by the output of phaselocked loop Electric analog-to-digital conversion module described in signal input, as the sampling clock of electric analog-to-digital conversion module, makes electric analog-digital converter exist all the time The peak of filtered electric pulse is sampled；

Second comprises high stable clock source, laser instrument repetition rate lock, adjustable time delay and a phase-locked loop circuit, high Stabilizing clock source provides low phase noise, the clock signal of low jitter, and this clock signal is locked through described laser instrument repetition rate After determining device, the repetition rate that the described optical pulse sequence generator of input sends pulse train to it is adjusted, and is locked On high stable clock source；Adjustable time delay described in this clock signal input, described digital processing element controls adjustable prolonging When device time delay so as to be finely adjusted in a cycle, through when the clock signal delayed input phase-locked loop circuit again In, obtain a stable repetition rate and electric analog-digital converter sample rate identical pulse signal, for electric analog-to-digital conversion module Sampling clock is provided, so that the peak of electric analog-digital converter electric pulse all the time after the filtering is sampled.

4. the configurable optical analog to digital conversion device of frequency response according to claim 1 is it is characterised in that described electrofiltration The time domain width of ripple device impulse response is more than single sampling optical pulse time domain pulsewidth.

5. according to the configurable optical analog to digital conversion device of Claims 1-4 any one frequency response it is characterised in that whole be The frequency response of system is configured by adjusting Optical Sampling clock and electrical filter, system equivalent impulse response h_A(t) and Optical Sampling Clock time domain waveform p (t) and the impulse response h of described electrical filter_ET () meets relation：h_A(t)=Kp (- t) h_ET (), K is Constant.