CN105024672A - Fiber F-P cavity driving method with a linear compensation function based on DDS - Google Patents

Abstract

The invention provides a fiber F-P cavity driving method with a linear compensation function based on a DDS. The method comprises: a FPGA establishes a ROM table of the DDS and stores the ROM table as a sawtooth wave digital signal of a driving power supply; and the sawtooth wave digital signal is subjected to frequency and phase control and digital-to-analog conversion, then is amplified and finally generates a sawtooth wave driving power supply matching the F-P cavity. The method has characteristics of high accuracy and high applicability, and may flexibly perform linear compensation according to different fiber F-P cavity piezoelectric ceramic characteristics.

Description

Based on the fiber F-P cavity driving method with linear compensation function of DDS

Technical field

The present invention relates to technical field is the fiber F-P cavity driving method with linear compensation function based on DDS.

Background technology

Along with the develop rapidly of fiber optic communication field, existing define a huge industrial structure.Meanwhile, optical fiber sensing technology also moves to maturity gradually.The device of this field core, as bifurcation multiplex apparatus and optical switch all relate to fiber F-P cavity.On the other hand, at sensory field of optic fibre, fiber F-P cavity is then an of paramount importance type optical fiber transducer, and sensor-based system is to the core component of signal receiving and fiber F-P cavity.Have a lot to the driving method of fiber F-P cavity at present, as driven by DDS method and use this patent linear compensation method then have no report.

Indication fiber F-P cavity of the present invention drives the drive power supply for piezoelectric ceramics for being carried in encapsulation F-P cavity.F-P cavity is filtering device, and indication fiber F-P cavity of the present invention is optical filter, as length scanning function element.The characteristic of such tunable fiber F-P cavity is as Fig. 1.Under sawtooth waveforms driving voltage, in the sawtooth waveforms rising edge stage, the centre wavelength through spectrum of sawtooth waveforms is along with magnitude of voltage linear change.But due to the hesitation that piezoelectric ceramic has, nonlinear distortion can be brought to driving power.Therefore, the linear compensation function that the present invention has has its Practical significance.

DDS(Direct Digital Frequency Synthesizer) i.e. Direct Digital Frequency Synthesizers, it is a kind of novel frequency synthesis technique, there is opposite band roomy, frequency switching time is short, the advantages such as the high and phase continuity of resolution is good, be easy to the numerical control modulation realizing frequency, phase place and amplitude, be widely used in the communications field.The basic block diagram of DDS as shown in Figure 2.

DDS is primarily of phase register, and frequency control word, waveform look-up table ROM and DAC transducer are formed, and phase register is made up of adder and register.Often carry out a clock, the phase data that frequency control word and phase register export just is added by adder, the result be added feeds back to again the data input pin of phase register, continue under the effect of next clock pulse to make adder to be added with frequency control word, like this, phase register, under the effect of clock, constantly carries out linear phase to frequency control word and adds up.And the output data of phase register, as the phase sample address of wave memorizer, so just the waveform sample values be stored in waveform look-up table can be found out through tabling look-up, complete the conversion of phase place to amplitude, DAC transducer is sent in the output of waveform look-up table, converts digital signal to analog signal output by DAC transducer.

In existing article, the linear compensation method of general employing has two kinds, the PID that a kind of algorithm for complexity and hardware complete jointly controls automatically, this method is too loaded down with trivial details, another kind of then be utilize contrafunctional method to change value in waveform look-up table, but the hesitation of PZT, temperature drift and crawling effect make actual driving voltage waveform cannot represent with a specific function, in this way not there is stronger actual operation.

Summary of the invention

The present invention proposes a kind of fiber F-P cavity driving method with linear compensation function based on DDS, this method of putting has the feature of high accuracy and high relevance grade, can carry out linear compensation flexibly according to the characteristic of different fiber F-P cavity piezoelectric ceramic.

The present invention adopts technical scheme to be: a kind of fiber F-P cavity driving method with linear compensation function based on DDS, it is characterized in that: it comprises the corresponding numerical value of signal waveform that FPGA built-in ROM table carrys out driving power required for storing fiber optic F-P cavity, value in ROM table passes through frequency, after phase control, 0-5V sawtooth voltage is converted to by analog-digital chip TLC5615, after amplification chip LM358 amplifies, generate the sawtooth waveforms driving power that 0-18V is matched with F-P cavity, the PZT of fiber F-P cavity has hesitation, show corresponding linear waveform by Real output waveform with ROM and there is nonlinear effect, therefore need to carry out linear compensation to driving power waveform.

Described fiber F-P cavity is the FFP-TF type of micro-optic company and is encapsulated in PZT, it is characterized in that needs 0 ~ 18V sawtooth waveforms power drives;

Described TLC5615 is the analog-digital chip of 10 precision, and its function is that the value be stored in the ROM table of DDS is converted to corresponding magnitude of voltage;

Described DDS is that FPGA inside is set up, the value that the 0-1023 that in DDS, in ROM, storage corresponds to 0-18V driving voltage linearly increases.This value sends TLC5615 to and carries out voltage transitions after phase place and frequency modulation(FM).

Advantage of the present invention is: this method of putting has the feature of high accuracy and high relevance grade, can carry out linear compensation flexibly according to the characteristic of different fiber F-P cavity piezoelectric ceramic.

Accompanying drawing explanation

Fig. 1 is the centre wavelength position corresponding diagram of F-P cavity driving voltage value of the present invention and transmitted light.

Fig. 2 is the schematic diagram of DDS of the present invention.

Fig. 3 is linear compensation schematic diagram of the function of the present invention.

Embodiment

Based on the fiber F-P cavity driving method with linear compensation function of DDS, to it is characterized in that: the ROM comprising the built-in DDS of FPGA stores as the sawtooth waveforms digital signal of driving power, by generating by analog-digital chip TLC5615 the sawtooth waveforms driving power being matched with F-P cavity after amplifying after frequency, phase control.

DDS of the present invention is built-in by FPGA, it is characterized in that the required sawtooth waveforms numerical value exported of employing ROM table storage, by exporting after frequency and phase-modulation, being changed and amplify sawtooth waveforms driving power needed for rear generation by TLC5615.

Driving method of the present invention has linear compensation function, has hesitation at the PZT of encapsulation F-P cavity, and stored waveform numerical value corresponding in being shown by difference ratio modified R OM, carries out linear compensation to driving power waveform.

The present invention is the tunable fiber F-P cavity (FFP-TF) for micro-optic company used in experiment, and driving power needed for it is 0 ~ 18V sawtooth voltage signal.The DAC chip TLC5615 precision used due to this experiment is 10bit, and the storing value namely in waveform look-up table is not 0 ~ 1024 not etc.Do not considering that nonlinear effect is, the value in ROM table and the magnitude of voltage direct proportionality of output.

But, as shown in Figure 3, owing to there is the nonlinear effects such as hesitation, distortion that can be certain to real waveform generation, therefore need to carry out linear compensation.

Based on the deficiency of other compensation methodes mentioned in specification technical background, the present invention proposes a kind of linear compensation method as shown in Figure 3.

Wherein, l _afor the rising edge of the sawtooth waveforms of desirable linear growth, l _bfor the actual waveform that may occur.Then there is relation:

(formula 1)

Suppose:

(formula 2)

Then revise as follows:

(formula 3)

Change by simple the value needing in ROM table to compensate like this, linear compensation can be carried out to driving power signal flexibly.

Claims (3)

1. the fiber F-P cavity driving method with linear compensation function based on DDS, it comprises the corresponding numerical value of signal waveform that FPGA built-in ROM table carrys out driving power required for storing fiber optic F-P cavity, value in ROM table passes through frequency, after phase control, 0-5V sawtooth voltage is converted to by analog-digital chip TLC5615, after amplification chip LM358 amplifies, generate the sawtooth waveforms driving power that 0-18V is matched with F-P cavity, the PZT of fiber F-P cavity has hesitation, show corresponding linear waveform by Real output waveform with ROM and there is nonlinear effect, therefore need to carry out linear compensation to driving power waveform.

2. a kind of fiber F-P cavity driving method with linear compensation function based on DDS according to claim 1, is characterized in that:

Described fiber F-P cavity is the FFP-TF type of micro-optic company and is encapsulated in PZT, it is characterized in that needs 0 ~ 18V sawtooth waveforms power drives;

Described TLC5615 is the analog-digital chip of 10 precision, and its function is that the value be stored in the ROM table of DDS is converted to corresponding magnitude of voltage;

Described DDS is that FPGA inside is set up, and the value that the 0-1023 that in DDS, in ROM, storage corresponds to 0-18V driving voltage linearly increases, this value sends TLC5615 to and carries out voltage transitions after phase place and frequency modulation(FM).

3. a kind of fiber F-P cavity driving method with linear compensation function based on DDS according to claim 1, have linear compensation function, specific implementation step is as follows:

In ideal voltage value Y and ROM shows there is relation in respective value X:

(formula 1)

Suppose:

(formula 2)

Then revise as follows:

(formula 3)

Change by simple the value needing in ROM table to compensate like this, linear compensation can be carried out to driving power signal flexibly.