CN103053142A - Method, device, and transmission system for generating quadrature amplitude modulation signal - Google Patents

Method, device, and transmission system for generating quadrature amplitude modulation signal Download PDF

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Publication number
CN103053142A
CN103053142A CN2012800004660A CN201280000466A CN103053142A CN 103053142 A CN103053142 A CN 103053142A CN 2012800004660 A CN2012800004660 A CN 2012800004660A CN 201280000466 A CN201280000466 A CN 201280000466A CN 103053142 A CN103053142 A CN 103053142A
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modulator
signals
signal
level
level signal
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延双毅
吕超
刘伯涛
刘磊
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Huawei Technologies Co Ltd
Hong Kong Polytechnic University HKPU
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Huawei Technologies Co Ltd
Hong Kong Polytechnic University HKPU
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/505—Laser transmitters using external modulation
    • H04B10/5053—Laser transmitters using external modulation using a parallel, i.e. shunt, combination of modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/54—Intensity modulation
    • H04B10/541—Digital intensity or amplitude modulation

Abstract

Provided are a method, device, and transmission system for generating a quadrature amplitude modulation signal. In the invention, a low-cost dual-drive optical quadrature (IQ) modulator is used to generate a quadrature amplitude modulation signal, reducing the cost of generating a quadrature amplitude modulation signal. Moreover, because two-level electrical drive signals are used, control of only two level signals is required, thereby reducing system requirements for drive signals and enhancing the quality of the quadrature amplitude modulation signal generated.

Description

The method of generating orthogonal am signals, device and transmission system
Technical field
The present invention relates to signal modulation technique, relate in particular to a kind of method, device and transmission system of generating orthogonal am signals.
Background technology
Along with the development of information technology, express network, mobile network progressively popularize, and new network is used and continued to bring out, so that internet traffic continues to keep rapid growth.
On the one hand, for the reply network traffics increase the huge transmission pressure that brings, the transport service of network system is also constantly being upgraded, to improve the transmission capacity of existing network; On the other hand, because based on the progress of the Digital Signal Processing of DSP (Digital Signal Processor, digital signal processor), so that adopt the transmission network of high order modulation format signal and coherent detection technology to become possibility.This transmission network has higher spectrum efficiency, can increase exponentially network transmission capacity at existing network.
Transmission system based on single ripple 100Gbit/s of palarization multiplexing quarternary phase-shift keying (QPSK) (Polarization-multiplexed Quadrature Phase Shift Keying, PM-QPSK) modulation format has progressively realized commercial at present.Follow-on backbone transport network requires the transmission capacity of the single ripple of system will reach 200Gbit/s even higher.Therefore studying the novel modulation format with higher spectrum efficiency is one of focus of current optical transport network research.1 6QAM (Quadrature Amplitude Modulation, quadrature amplitude modulation) modulation format, each symbol can transmit the information of four bits, compare the QPSK modulation format, having increased exponentially the spectrum efficiency of transmission system, is the important optical modulation formats that realizes optical transport network of future generation.
In the 16QAM transmission system, transmitting terminal generates 16QAM form light signal by the level signal of precoding generation multichannel by electrooptic modulator.Light signal adopts coherent receiver to receive through after the Optical Fiber Transmission, thereby recovers the signal before the precoding.
When generating 16QAM form light signal, need to modulate amplitude and the phase place of light, thereby form planisphere.The transmission system transmitter is that the part of most critical is how level signal to be loaded into light signal to get in the transmitting terminal, realizes the modulation of 16QAM.
In the existing 16QAM signal generating technique, adopt the level signal with four level to drive single-ended IQ modulator, generate the 16QAM signal.
The major defect of prior art is to adopt four level signals as driving.And the performance of four level signals directly affects the quality of the 16QAM signal of generation, and the generation of four level signals, and transmission and amplification are all very difficult.And four level signals are more sensitive for electrical noise, and two level signals of bandwidth ratio require high, and the particularly amplification of four level signals requires amplifier to have the very high linearity.
In order to address these problems, usually can improve the quality of four level signals by adopting DAC chip or additive method in the laboratory, still expensive, the high complexity owing to DAC makes it be difficult to extensive use in real system.
Summary of the invention
The embodiment of the invention provides a kind of method, device and transmission system of generating orthogonal am signals, for reducing the cost of generating orthogonal am signals, improves the quality of quadrature amplitude modulation signal.
The method of a kind of generating orthogonal am signals that the embodiment of the invention provides comprises:
Receive two groups of level signals, every group of level signal comprises two different level signals of amplitude, and the amplitude of described two level signals satisfies
Figure BDA00001850270400021
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πBe two half-wave voltages of driving light positive friendship IQ modulator;
Utilize and describedly two drive the IQ modulator described two groups of level signals are loaded on the light signal, synthesize and obtain quadrature amplitude modulation signal.
The device of a kind of generating orthogonal am signals that the embodiment of the invention provides comprises:
Two light positives that drive are handed over the IQ modulator, comprise a defeated light inlet, a defeated light-emitting window, two intensity modulators and a phase-modulator, and each intensity modulator has a pair of differential driving electrical interface;
The level signal driver, link to each other with the differential driving electrical interface of described two intensity modulators, be used to and describedly two drive the IQ modulator two groups of level signals are provided, every group of level signal inputted a pair of differential driving electrical interface, every group of level signal comprises two different level signals of amplitude, and the amplitude of described two level signals satisfies
Figure BDA00001850270400031
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πBe described two half-wave voltages of driving the IQ modulator.
The transmission system of a kind of quadrature amplitude modulation signal that the embodiment of the invention provides, comprise sending ending equipment and receiving device, described sending ending equipment is connected by optical fiber with described receiving device, wherein, described sending ending equipment comprises the device of above-mentioned generating orthogonal am signals, and the quadrature amplitude modulation signal that the device of described generating orthogonal am signals generates sends to described receiving device by described optical fiber.
Method, device and the transmission system of the generating orthogonal am signals that the embodiment of the invention provides, by adopting lower-cost two IQ modulator generating orthogonal am signals that drives, reduced the cost of generating orthogonal am signals, and, owing to adopt the electric drive signal of two level, simplify system to driving the requirement of signal, effectively improved the quality of the quadrature amplitude modulation signal that generates.
Description of drawings
The flow chart of the method for the generating orthogonal am signals that Figure 1A provides for the embodiment of the invention;
Figure 1B is the planisphere of the 16QAM signal that method can generate shown in Figure 1A;
The structural representation of the device of the generating orthogonal am signals that Fig. 2 A provides for the embodiment of the invention;
The structural representation of level signal driver in the device of the generating orthogonal am signals that Fig. 2 B provides for the embodiment of the invention;
Two internal structure schematic diagrames that drive the IQ modulator in the device of the generating orthogonal am signals that Fig. 3 provides for the embodiment of the invention;
Two load mode schematic diagrames that drive the inner MZM modulator driving signal of IQ modulator of the generating orthogonal am signals that Fig. 4 A provides for the embodiment of the invention;
The device of the generating orthogonal am signals that Fig. 4 B embodiment of the invention provides is used for the schematic diagram of Bias point control;
Fig. 5 is the schematic diagram that prior art generates 16QAM;
The structural representation of the transmission system of the quadrature amplitude modulation signal that Fig. 6 provides for the embodiment of the invention.
Embodiment
The flow chart of the method for the generating orthogonal am signals that Figure 1A provides for the embodiment of the invention.In the embodiment of the invention, the transmitting terminal of the transmission system of 16QAM modulation format adopts two IQ modulators that drive to generate the 16QAM signal, and shown in Figure 1A, the method for generating orthogonal am signals comprises:
Step 11, two groups of level signals of reception, every group of level signal comprises two different level signals of amplitude, and the amplitude of these two level signals satisfies the relational expression of setting:
Figure BDA00001850270400041
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πBe two half-wave voltages of driving light positive friendship (In-phase/Quadrature-phase, IQ) modulator.
Step 12, utilize and twoly to drive the IQ modulator and these two groups of level signals are loaded on the light signal the synthetic quadrature amplitude modulation signal that obtains.For example, through above-mentioned steps 11, step 12, obtain the planisphere of the 16QAM signal shown in Figure 1B.Wherein, the intensity modulator in the two IQ of driving modulators can be MZM modulator (Mach-Zehnder Modulator).
In the embodiment of the invention, by two drivings of driving the electric drive signal of IQ modulator and two level, generated 16QAM.And in the prior art, the 16QAM signal modulator produces respectively the electrical modulation with four amplitudes on the IQ both direction, so that produce respectively the modulation with four amplitudes on two arms, namely adopting four level signals at each arm is in order to obtain the 4APSK modulation signal, to obtain the 16QAM light signal through after synthetic.And four level signals are usually synthetic by two level signals, and because the 16QAM signal quality that produces is subjected to four level signal performance impacts very large, four level signals after synthetic need to adopt high-quality linear amplifier to amplify, and traditional electric amplifier can't be realized high-quality linear the amplification, in the situation of equal baud rate, four level signals are compared two level signals and are required the electric device bandwidth wider in addition.Therefore, under same rate behavior, four level signals are higher to bandwidth requirement than two level signals, device performance required high.The embodiment of the invention adopts two drive IQ modulator and two level signals drivings, four level signals have been avoided using, and because two level signals are easy to realization and stable performance, effectively reduced the cost of generating orthogonal am signals, improved the quality of generating orthogonal am signals.
The method of the generating orthogonal am signals that the embodiment of the invention provides also can comprise: the bias point that this pair drive two intensity modulators in the IQ modulator is set all is positioned at smallest point (minimum), to be used for generating square 16QAM (Square 16QAM) signal.Wherein, smallest point is the bias point that makes MZM intensity modulator power output minimum.
The method of the generating orthogonal am signals that the embodiment of the invention provides also can comprise: the bias point that this pair drive an intensity modulator in the IQ modulator is set is positioned at smallest point, the bias point of another intensity modulator departs from smallest point, to be used for generating hexagon 16QAM (Hexagonal 16QAM) signal.
Distance between hexagon 16QAM signal constellation point and the adjacent constellation point equates that all it is compacter to compare square 16QAM constellation point, is a kind of 16QAM signal that energy efficiency is arranged most.
The method of the generation 16QAM that said method embodiment provides has the advantage that system is simple, be easy to realize compared to existing technology, has effectively overcome the shortcoming of prior art scheme.
One of ordinary skill in the art will appreciate that: all or part of step that realizes above-mentioned each embodiment of the method can be finished by the relevant hardware of program command.Aforesaid program can be stored in the computer read/write memory medium.This program is carried out the step that comprises above-mentioned each embodiment of the method when carrying out; And aforesaid storage medium comprises: the various media that can be program code stored such as ROM, RAM, magnetic disc or CD.
The structural representation of the device of the generating orthogonal am signals that Fig. 2 A provides for the embodiment of the invention.In the embodiment of the invention, the device of generating orthogonal am signals is used for realizing the method for above-mentioned Figure 1A illustrated embodiment, shown in Fig. 2 A, comprising: the two IQ of driving modulators 21 and level signal driver 22.
The two IQ of driving modulators 21 comprise a defeated light inlet 211, a defeated light-emitting window 212, two intensity modulators 213 and a phase-modulator 214, and each intensity modulator has a pair of differential driving electrical interface 215.Defeated light inlet 211 can receive the output optical signal of continuous wave laser, defeated light-emitting window 212 output 16QAM signals, and intensity modulator 213 can be the MZM modulator.One road light signal carries out phase-modulation to phase-modulator 214 for inciting somebody to action wherein, makes phase phasic difference 90 degree of this road light signal and another road light signal.
The level signal that two two pairs of differential driving electrical interfaces 215 that drive the IQ modulator receive corresponding to I axle and Q axle.
Level signal driver 22 links to each other with the differential driving electrical interface 215 of these two intensity modulators 213, be used to this pair to drive IQ modulator 21 two groups of level signals are provided, every group of level signal inputted a pair of differential driving electrical interface, every group of level signal comprises two different level signals of amplitude, and the amplitude of these two level signals satisfies
Figure BDA00001850270400061
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πDrive the half-wave voltage of IQ modulator for this pair.
Level signal driver 22 can be four road electric drives, can produce two groups of level signals.Four road signals of telecommunication waiting for transmission produce suitable driving signal through level signal driver 22, drive two IQ modulators that drive.Level signal driver 22 is input as binary system high-speed level signal, is output as the binary-level signal of amplification.
Shown in Fig. 2 B, signal of telecommunication driver can comprise amplitude controller and two kinds of devices of synchronous control unit, and wherein amplitude controller mainly is responsible for the amplitude of control four road signals, and synchronous control unit is controlled the synchronous of four road signals, namely guarantees four tunnel signal alignment.
The output of above-mentioned four road electric drives is connected with two pairs of differential driving electrical interfaces 215 of IQ modulator.Level signal driver 22 is input in one group of level signal of the axial differential driving electrical interface of I axle or Q, and comprise two different level signals of amplitude: the amplitude of one road high level signal is V H, the amplitude of one road low level signal is V LThe amplitude adjusted of level signal can adopt decay or change driver and gain to realize.
Two internal structure schematic diagrames that drive the IQ modulator in the device of the generating orthogonal am signals that Fig. 3 provides for the embodiment of the invention.In the embodiment of the invention, the generation of 16QAM signal is realized by two IQ modulators modulate continuous lights that drive.As shown in Figure 3, load two level signals with different amplitudes at two arms of two MZM modulators of the two IQ of driving modulators inside, generated the 16QAM signal.
Two load modes that drive the inner MZM modulator driving signal of IQ modulator have been provided among Fig. 4 A.As shown in Fig. 4 A, two both arms I that drive the MZM modulator of IQ modulator inside +Arm, I -Arm, or Q +Arm, Q -Respectively loading amplitude is V on the arm HAnd V LSignal, V wherein HGreater than V LThat is to say I +Arm or Q +The loading amplitude is V on the arm HLevel signal, I -Arm or Q -The loading amplitude is V on the arm LLevel signal.Owing to adopt different driving signals, this MZM modulator device is all modulated phase place and the amplitude of the light of this MZM modulator of process, has formed the 4APSK signal.For the modulation point that guarantees to form has identical interval at the I direction of principal axis, require MZM two arms institute plus signal amplitude to satisfy:
Figure BDA00001850270400062
Wherein, V πHalf-wave voltage for the MZM modulator.
Because two MZM modulator two arm load signal amplitudes of driving are different, output through the light signal of ovennodulation showing as constellation point and I axle and occurred the skew of a bit, shown in Fig. 4 A.The side-play amount size of I axle is relatively:
I offset = | imag ( E out ( t ) E in ( t ) ) | = sin V H + V L 4 V π / π sin V H - V L 4 V π / π
On the I of the two IQ of driving modulators arm and Q arm, all adopt in the same way modulation, the result as shown in Figure 1B, the two IQ of driving modulators are output as the 16QAM signal.
Because extra phase-modulation, there is certain skew at the relative IQ plane coordinates of the constellation point center of the 16QAM signal of generation.This skew is little for the systematic function impact, processes by simple signal at receiving terminal and can remove this skew.
Adopt said structure, can realize the generation of square 16QAM and hexagon 16QAM signal.
Particularly, shown in Fig. 4 B, the 16QAM signal feeds back to the Bias point control module by PD, and then the Bias point control module is controlled the bias point of IQ modulator according to feedback signal, thereby produces different 16QAM signals.Bias point such as built-in two the MZM modulators of IQ modulator is positioned at smallest point, can generate square 16QAM signal according to the driving method of Fig. 3.
Any one MZM modulator bias point of regulating in the IQ modulator departs from smallest point, and another MZM modulator still is offset to smallest point, then can generate hexagon 16QAM signal.
Said apparatus embodiment adopts two level signals to drive, and drives signal and simplifies, and the reduction system is to drive bandwidth, and the requirements such as the linearity have also reduced the cost that generates the 16QAM signal.In the various schemes that adopt the IQ modulation, said method and device embodiment compare four level signals of the prior art shown in Figure 5 and drive and generate the 16QAM signal, require lowlyer for bandwidth of a device, cost each side, have certain advantage.
The structural representation of the transmission system of the quadrature amplitude modulation signal that Fig. 6 provides for the embodiment of the invention.As shown in Figure 6, the transmission system of quadrature amplitude modulation signal comprises sending ending equipment 61 and receiving device 62, and this sending ending equipment 61 links by optical fiber 63 with this receiving device 62.Wherein, this sending ending equipment 61 comprises 16QAM modulator 611.16QAM modulator 611 can be the device of arbitrary generating orthogonal am signals that above-described embodiment provides, and the quadrature amplitude modulation signal that the device of this generating orthogonal am signals generates sends to this receiving device by this optical fiber 63.Here 16QAM modulator 611 can be square 16QAM modulator, also can be hexagon 16QAM modulator.
Sending ending equipment 61 changes data into level signal, and modulates by 16QAM modulator 611, obtains the 16QAM signal.This 16QAM signal has carried as to have carried the light signal of data, sends to receiving device 62 by optical fiber 63.
After receiving device 62 receives the 16QAM signal, utilize the 16QAM demodulator that the 16QAM signal is carried out demodulation, isolate level signal, obtain data.
In the embodiment of the invention, the transmission system of quadrature amplitude modulation signal is by adopting two IQ modulators that drive, and utilize two level signals namely the electric drive signal of two level drive, reduced the cost of generating orthogonal am signals, improved the quality of quadrature amplitude modulation signal.
It should be noted that at last: above each embodiment is not intended to limit only in order to technical scheme of the present invention to be described; Although with reference to aforementioned each embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment puts down in writing, and perhaps some or all of technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the scope of various embodiments of the present invention technical scheme.

Claims (7)

1. the method for a generating orthogonal am signals is characterized in that, comprising:
Receive two groups of level signals, every group of level signal comprises two different level signals of amplitude, and the amplitude of described two level signals satisfies
Figure FDA00001850270300011
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πBe two half-wave voltages of driving light positive friendship IQ modulator;
Utilize and describedly two drive the IQ modulator described two groups of level signals are loaded on the light signal, obtain quadrature amplitude modulation signal.
2. the method for generating orthogonal am signals according to claim 1 is characterized in that, also comprises: described two bias point that drives two intensity modulators in the IQ modulator is set all is positioned at smallest point.
3. the method for generating orthogonal am signals according to claim 1, it is characterized in that, also comprise: described two bias point that drives an intensity modulator in the IQ modulator is set is positioned at smallest point, the bias point of another intensity modulator departs from smallest point.
4. the device of a generating orthogonal am signals is characterized in that, comprising:
Two light positives that drive are handed over the IQ modulator, comprise a defeated light inlet, a defeated light-emitting window, two intensity modulators and a phase-modulator, and each intensity modulator has a pair of differential driving electrical interface;
The level signal driver, link to each other with the differential driving electrical interface of described two intensity modulators, be used to and describedly two drive the IQ modulator two groups of level signals are provided, every group of level signal inputted a pair of differential driving electrical interface, every group of level signal comprises two different level signals of amplitude, and the amplitude of described two level signals satisfies
Figure FDA00001850270300012
Wherein, V HBe the high level signal amplitude in every group of level signal, V LBe the low level signal amplitude in every group of level signal, V πBe described two half-wave voltages of driving the IQ modulator.
5. the device of generating orthogonal am signals according to claim 4 is characterized in that, the bias point of described two intensity modulators all is positioned at smallest point.
6. the device of generating orthogonal am signals according to claim 4 is characterized in that, described two bias points that drive an intensity modulator in the IQ modulator are positioned at smallest point, and the bias point of another intensity modulator departs from smallest point.
7. the transmission system of a quadrature amplitude modulation signal, comprise sending ending equipment and receiving device, described sending ending equipment is connected by optical fiber with described receiving device, it is characterized in that, described sending ending equipment comprises the device of each described generating orthogonal am signals of the claims 4-6, and the quadrature amplitude modulation signal that the device of described generating orthogonal am signals generates sends to described receiving device by described optical fiber.
CN2012800004660A 2012-03-14 2012-03-14 Method, device, and transmission system for generating quadrature amplitude modulation signal Pending CN103053142A (en)

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Application publication date: 20130417