Apparatus and method for monitoring analog characteristic of optical transmitter, and optical transmitter

Abstract

To provide an apparatus, method and optical transmitter for monitoring an analog characteristic of an optical transmitter in which: analog characteristic information of the optical transmitter is extracted by using the correlation quantity between the to-be-measured optical signal and the modulated local signal; the required hardware cost is much lower than that of a conventional broadband receiver; and, because there is no need to perform complex digital signal processing (DSP), power consumption is reduced greatly.SOLUTION: The method comprises: inputting a first signal to a first electro-optical converter to obtain a to-be-measured optical signal; inputting a second signal to a second electro-optical converter to obtain a modulated local signal, so that the second signal is determined according to the first signal and a to-be-monitored analog characteristic of the first electro-optical converter; performing correlation processing on the to-be-measured optical signal and the modulated local signal to obtain at least one correlation quantity; and estimating an analog characteristic of the first electro-optical converter according to the correlation quantity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of optical communications. [Background technology]

[0002] With the development of communication technology, transceiver analog characteristic imperfections have increasingly become the main damage affecting the transmission performance of optical communication systems. Taking the 64G Baud 64QAM signal in a coherent optical communication system as an example, even a slight IQ (In-phase / Quadrature) amplitude imbalance (e.g., 0.5 dB), IQ phase imbalance (e.g., 4°), or IQ skew (e.g., 0.7 ps) in the transmitter can result in a cost of 0.5 dB in the optical signal-to-noise ratio (OSNR). Therefore, it is necessary to easily and accurately monitor and calibrate the analog characteristic imperfections of optical transmitters.

[0003] Currently, the optical transmitter's imperfections can be estimated and compensated for based on the receiver's equalizer, and the transmitter's imperfections can be dynamically compensated and estimated at the receiving end. However, this method is not stable because the range of imperfections that can be compensated and estimated is limited and it functions after carrier phase recovery, so it is susceptible to channel impairments, receiver optical signal-to-noise ratio, and the working state of receiver digital signal processing (DSP).

[0004] It should be noted that the introduction of the above background art is intended to clearly and completely explain the technical solutions of the present invention and to facilitate understanding by those skilled in the art, and these technical solutions described in the background art of the present invention should not be construed as being known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0005] The inventor discovered that since the transmitter analog characteristic defects are at the transmitting end, the compensation effect at the transmitting end is better than that at the receiving end. However, if the impairment coefficient estimated by the remote receiver is fed back to the transmitter for use in compensating for the analog characteristic defects, additional communication resources need to be occupied and implementation is inconvenient. Furthermore, if an additional full-featured broadband receiver is placed at the transmitting end to monitor the transmitter analog characteristic, the hardware cost and power consumption of the required broadband receiver and high-speed analog-to-digital converter will be very high.

[0006] In view of at least one of the above technical problems, embodiments of the present invention provide an apparatus and method for monitoring analog characteristics of an optical transmitter, and an optical transmitter, which uses a low-speed optoelectronic device or an electrical device to perform correlation processing to obtain a correlation amount between an optical signal to be measured and a modulated local signal (i.e., a modulated local signal), and can calculate and estimate the analog characteristics of the transmitter to be measured based on the correlation amount. [Means for solving the problem]

[0007] According to one aspect of an embodiment of the present invention, there is provided an optical transmitter analog characteristic monitoring apparatus, which comprises: a first input unit for inputting a first signal into a first electro-optical converter to obtain an optical signal to be measured; a second input unit for inputting a second signal to a second electro-optical converter to obtain a modulated local signal, the second signal being determined based on the first signal and the monitored analog characteristics of the first electro-optical converter; a correlation unit that performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and An estimation unit is included for estimating an analog characteristic of the first electrical-optical converter based on the correlation amount.

[0008] According to another aspect of an embodiment of the present invention, there is provided an optical transmitter analog characteristic monitoring method, which includes: inputting the first signal into a first electrical-optical converter to obtain an optical signal to be measured; inputting a second signal into a second electro-optical converter to obtain a modulated local signal, wherein the second signal is determined based on the first signal and the analog characteristics monitored by the first electro-optical converter; performing a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and and estimating an analog characteristic of the first electrical-to-optical converter based on the correlation amount.

[0009] According to another aspect of an embodiment of the present invention, there is provided an optical transmitter, the optical transmitter including a first electrical-to-optical converter and a second electrical-to-optical converter; a first signal is input to the first electro-optical converter to obtain an optical signal to be measured, and a second signal is input to the second electro-optical converter to obtain a modulated local signal, wherein the second signal is determined based on the first signal and the analog characteristic to be monitored of the first electro-optical converter; The optical transmitter further includes a monitoring device that performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity, and estimates the analog characteristics of the first electrical-optical converter based on the correlation quantity. [Effects of the Invention]

[0010] The advantageous effects of the embodiment of the present invention are at least as follows: the correlation between the optical signal to be measured and the modulated local signal is used to extract analog characteristic information of the optical transmitter, which reduces the required hardware cost significantly compared to a conventional broadband receiver, and eliminates the need for complex digital signal processing (DSP), thereby significantly reducing power consumption.

[0011] The following description and reference to the drawings disclose in detail particular embodiments of the present invention, illustrating ways in which the principles of the present invention may be employed, but the scope of the present invention is not limited thereto, and various changes, modifications, and alternatives may be included within the scope of the appended claims.

[0012] Additionally, features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, may be combined with features in the other embodiments, or may be substituted for features in the other embodiments.

[0013] It should be noted that when used in this specification, terms such as "comprise / have" refer to the presence of a feature, element, step, or assembly, but do not exclude the presence or addition of one or more other features, elements, steps, or assemblies. [Brief explanation of the drawings]

[0014] Elements and features described in one drawing or one embodiment of the invention may be combined with elements and features shown in one or more other drawings or embodiments, and in the drawings, like reference numerals are used to indicate corresponding parts in several drawings and to indicate corresponding parts used in multiple embodiments.

[0015] The included drawings are used to provide a further understanding of the embodiments of the present invention, and these drawings constitute a part of this specification, illustrate embodiments of the present invention, and together with the written description, serve to explain the principles of the present invention. Also, it is apparent that the drawings described below are only for illustrating some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without any creative effort. [Figure 1] 1 is a diagram illustrating a method for monitoring analog characteristics of an optical transmitter according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing a parallel modulation correlation processing-based transmitter analog characteristic monitoring device according to an embodiment of the present invention. [Figure 3A] 3A-3C illustrate different types of first electrical-optical converters in embodiments of the present invention; [Figure 3B] 3A-3C illustrate different types of first electrical-optical converters in embodiments of the present invention; [Figure 3C] 3A-3C illustrate different types of first electrical-optical converters in embodiments of the present invention; [Figure 3D] 3A-3C illustrate different types of first electrical-optical converters in embodiments of the present invention; [Figure 4A] 3A and 3B are diagrams illustrating first electro-optical converters with different polarization structures in embodiments of the present invention. [Figure 4B] 3A and 3B are diagrams illustrating first electro-optical converters with different polarization structures in embodiments of the present invention. [Figure 5A] 3A and 3B are diagrams illustrating first electro-optical converters with different modulation structures in embodiments of the present invention. [Figure 5B] 3A and 3B are diagrams illustrating first electro-optical converters with different modulation structures in embodiments of the present invention. [Figure 5C] 3A and 3B are diagrams illustrating first electro-optical converters with different modulation structures in embodiments of the present invention. [Figure 6A] 3A-3C are diagrams showing different types and structures of second electro-optical converters in embodiments of the present invention; [Figure 6B] 3A-3C are diagrams showing different types and structures of second electro-optical converters in embodiments of the present invention; [Figure 6C] 3A-3C are diagrams showing different types and structures of second electro-optical converters in embodiments of the present invention; [Figure 6D] 3A-3C are diagrams showing different types and structures of second electro-optical converters in embodiments of the present invention; [Figure 6E] 3A-3C are diagrams showing different types and structures of second electro-optical converters in embodiments of the present invention; [Figure 7] FIG. 10 is a diagram illustrating a correlation process in an embodiment of the present invention. [Figure 8] 3A-3C illustrate possible output ports of a first electrical-to-optical converter in an embodiment of the present invention. [Figure 9A]FIG. 2 illustrates an optical-electrical multiplier according to an embodiment of the present invention. [Figure 9B] FIG. 2 illustrates an optical-electrical multiplier according to an embodiment of the present invention. [Figure 9C] FIG. 2 illustrates an optical-electrical multiplier according to an embodiment of the present invention. [Figure 9D] FIG. 2 illustrates an optical-electrical multiplier according to an embodiment of the present invention. [Figure 10A] FIG. 1 illustrates an electrical averaging unit to which square wave multiplication and frequency shifting functions are added in an embodiment of the present invention. [Figure 10B] FIG. 1 illustrates an electrical averaging unit to which square wave multiplication and frequency shifting functions are added in an embodiment of the present invention. [Figure 11A] 2 is a diagram illustrating a first electro-optical converter and a second electro-optical converter according to an embodiment of the present invention; FIG. [Figure 11B] 2 is a diagram illustrating a first electro-optical converter and a second electro-optical converter according to an embodiment of the present invention; FIG. [Figure 12] 2 is a diagram illustrating a first electro-optical converter and a second electro-optical converter according to an embodiment of the present invention; FIG. [Figure 13] 2 is a diagram illustrating a first electro-optical converter and a second electro-optical converter according to an embodiment of the present invention; FIG. [Figure 14] FIG. 1 is a diagram showing a serial modulation correlation processing-based transmitter analog characteristic monitoring device according to an embodiment of the present invention. [Figure 15] FIG. 2 illustrates a first electrical-optical converter in an embodiment of the present invention. [Figure 16] FIG. 1 illustrates serial-based modulation and coherent detection in an embodiment of the present invention. [Figure 17] FIG. 10 is another diagram illustrating monitoring of transmitter analog characteristics in an embodiment of the present invention. [Figure 18] 1 is a diagram illustrating an optical transmitter analog characteristic monitoring device according to an embodiment of the present invention. [Figure 19] 1 is a diagram illustrating an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The foregoing and other features of the present invention will become more apparent from a consideration of the accompanying drawings and the following description. While the specification and drawings disclose particular embodiments of the present invention, they illustrate only some of the embodiments which may employ the principles of the present invention, and it is to be understood that the present invention is not limited to the described embodiments, but rather includes all modifications, variations, and alternatives which fall within the scope of the appended claims.

[0017] As is well known, correlation can be used to achieve equivalent post-reception sampling. Suppose there is an input pulse signal g(t), which is generated by a unit impulse pulse signal δ(t) through a shaping function g(t), and the signal after passing through a receiver with analog characteristics h′(t) is:

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[0022] Based on this, the signal transmitted by one real transmitter is

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[0025] Let h′(t)=h(-t), in this case,

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[0027] Obviously, receiving and sampling a single high-speed signal requires a high-speed receiver and a high-speed ADC, which means a fairly high hardware cost and power consumption. After converting to correlation, the integration operation (arithmetic) is equivalent to an averaging operation, so it can be realized with a low-speed device. Also, the multiplication operation can be completed using the natural physical properties of optical or optoelectronic devices. In this way, an equivalent receiver can be realized with a low-speed, low-power device.

[0028] The transmitted signal is a random signal, i.e.,

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[0030] In an embodiment of the present invention, a modulated local signal

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[0041] This makes it possible to discover the following: the correlation amount represents the value of the impulse response at time t when the first electro-optical modulator and the second electro-optical modulator are cascaded, and t depends on the relative delay between the signal to be measured and the correlated signal of the signal to be measured, or the relative delay between the optical signal to be measured and the modulated local signal. Therefore, when the object to be monitored is the impulse response when the first electro-optical converter and the second electro-optical converter are cascaded, the response can be obtained by correlation processing. Also, when the analog characteristics of the second electro-optical converter are acquired in advance, the analog characteristics of the first electro-optical converter can be calculated and estimated based on the correlation amount. When the analog characteristics of the second electro-optical converter are unknown but do not change with time or the environment, the correlation amount can be used to monitor changes in the analog characteristics of the first electro-optical converter with time or environmental temperature.

[0042] If a transmitter can be viewed as a superposition of multiple signals, such as the I path (also called a branch) and Q path of a coherent transmitter, by monitoring the I path once and the Q path once and comparing the two monitoring results, it is possible to obtain difference information between the I path and the Q path, i.e., IQ imbalance, even if the analog characteristics of the second electrical-to-optical converter are unknown. This is because the effect of the second electrical-to-optical converter on both the I and Q paths is the same. Similar cases include horizontal and vertical bidirectional (two-path) polarization, differences in the characteristics of different segments in a modulator consisting of multiple segments, differences between different bit paths within a modulator, differences in the analog characteristics between different sub-DACs of a time-interleaving digital-to-analog converter (TI-DAC), and differences in transmitter analog characteristics when different transmit symbol sequences are used under nonlinear conditions.

[0043] The above briefly describes the ideas of the embodiments of the present invention, and specific embodiments will be further described below.

[0044] <Example of the first aspect> An embodiment of the present invention provides an optical transmitter analog characteristic monitoring method. Figure 1 shows an optical transmitter analog characteristic monitoring method according to an embodiment of the present invention. As shown in Figure 1, the method includes the following steps: 101: inputting a first signal into a first electrical-optical converter to obtain an optical signal to be measured; 102: inputting a second signal into a second electro-optical converter to obtain a modulated local signal, wherein the second signal is determined according to the first signal and the analog characteristics of the first electro-optical converter being monitored; 103: performing a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and 104: Estimate the analog characteristics of the first electrical-optical converter based on the correlation amount.

[0045] Note that, although the above-described FIG. 1 is used to exemplify an embodiment of the present invention, the present invention is not limited thereto. For example, some of the above steps may be performed simultaneously or sequentially, and the order of operations may be appropriately adjusted, or some operations may be added or removed. Those skilled in the art may make appropriate modifications based on the above content without being limited to the description of the above-described FIG. 1.

[0046] In some embodiments, the correlation quantity represents a value at a first time of an impulse response when the first electrical-to-optical converter and the second electrical-to-optical converter are cascaded, and the first time depends on the relative delay between the first signal and the second signal.

[0047] In some embodiments, when a transmitter transmits at least two superimposed signals, each signal is monitored at least once to obtain at least two correlation quantities, and an analog characteristic of the first electrical-to-optical converter is estimated based on the at least two correlation quantities.

[0048] The following will first describe the configuration of an embodiment of the present invention. There are multiple specific implementation methods for correlation processing, which can be divided into parallel-based modulation (parallel modulation-based) and serial-based modulation (serial modulation-based) based on the hardware configuration. Below, the parallel modulation-based scheme will be described first.

[0049] In some embodiments, the first electrical-optical converter and the second electrical-optical converter are connected in parallel, the first electrical-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, the second electrical-optical converter generates the modulated local signal based on the optical carrier and the second signal, the optical signal to be measured and the modulated local signal are respectively input to an optical-electrical multiplier to generate a product electrical signal, and the product electrical signal is electrically averaged to generate the at least one correlation quantity.

[0050] 2 is a diagram showing a parallel modulation correlation processing-based transmitter analog characteristic monitoring device according to an embodiment of the present invention. As shown in FIG. 2, the device may include: First electrical-optical converter 201: the optical transmitter itself or only a part of the optical transmitter, whose analog characteristics are the target quantity to be monitored, generates an optical signal to be measured; a second electro-optical converter 202: generating a modulated local signal according to a correlation signal of the signal to be measured, the modulated local signal being correlated with the optical signal to be measured, the first electro-optical converter 201 and the second electro-optical converter 202 being in a parallel relationship; Correlation processor 203: performs correlation processing on the optical signal to be measured and the modulated local signal based on the low-speed optical-electrical device and the electrical device to obtain the correlation amount of the two signals; and Analog characteristic estimator 204: Estimates the analog characteristic of the first electrical-optical converter based on the signal correlation amount.

[0051] Although FIG. 2 illustrates exemplary structures for implementing analog characteristic monitoring of an optical transmitter, the present invention is not limited to these structures, and appropriate modifications can be made to these structures. Furthermore, all of the implementation methods of these modifications are included within the scope of the embodiments of the present invention.

[0052] 2, the first electrical-optical converter 201 modulates the signal to be measured A[n] to be transmitted and loads it onto an optical carrier, generates a corresponding optical signal to be measured, and provides it as feedback (provides it) to the correlation processor 203. The first electrical-optical converter 201 may be a complete optical transmitter, or may be only a part of an optical transmitter.

[0053] It should be noted that the present invention does not limit the type and structure of the first electrical-optical converter. For example, the physical material used by it may be lithium niobate, indium phosphide, silicon, etc. For example, it may be a coherent transmitter, an intensity-modulated transmitter, or even a combined (composite) signal transmitter based on a phase modulator or an optical frequency comb.

[0054] 3A to 3D are diagrams illustrating different types of first electrical-optical converters in embodiments of the present invention. The first electrical-optical converter 201 can be any one of the following: a coherent transmitter as shown in FIG. 3A, an intensity modulator as shown in FIG. 3B, a phase modulator as shown in FIG. 3C, and an optical frequency comb-based combination signal transmitter as shown in FIG. 3D.

[0055] Also, for example, the first electrical-optical converter 201 may be a transmitter that outputs only a single polarized signal, or may be a transmitter that outputs a dual polarized signal.

[0056] 4A and 4B are diagrams illustrating first electro-optical converters with different polarization structures in embodiments of the present invention. The first electro-optical converter 201 can be any one of the following: a single polarization electro-optical converter as shown in FIG. 4A and a dual polarization electro-optical converter as shown in FIG. 4B.

[0057] Also, for example, the first electro-optical converter 201 may further be based on a single-stage modulation structure, or may be based on a segmented multi-stage modulation structure, and the segmented design type may be of uniformly equal length (e.g., Thermometer) or unequal length (e.g., binary).

[0058] 5A to 5C are diagrams illustrating first electro-optical converters with different modulation structures in embodiments of the present invention. The first electro-optical converter 201 can be any one of the following: a single-stage electro-optical converter as shown in FIG. 5A, a multi-stage segmented electro-optical converter with unequal length segment design structure as shown in FIG. 5B, and a multi-stage segmented electro-optical converter with equal length segment design structure as shown in FIG. 5C.

[0059] If the response of the first electrical-optical converter is g(t), the optical signal to be measured that is generated can be simply expressed as:

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[0061] 2, the second electro-optical converter 202 loads the correlation signal B[n] of the signal to be measured onto an optical carrier, generates a modulated local signal, and feeds it back to the correlation processor 203. The type and structure of the second electro-optical converter 202 may also take a variety of forms. For example, it may be an MZ intensity modulator (MZM), an electro-absorption modulator (EAM), or a single phase modulator (PM), or it may be configured by cascading L (L≧2) equal-length or unequal-length segment modulators, or it may be formed by serially connecting modulators of different types (for example, a MZM or an EAM and a PM).

[0062] 6A to 6E are diagrams illustrating different types and structures of second electro-optical converters in embodiments of the present invention. The second electro-optical converter 202 can be any one of the following: a MZ-type intensity modulator with one segment as shown in FIG. 6A, an electro-absorption modulator as shown in FIG. 6B, a phase modulator as shown in FIG. 6C, a MZ-type intensity modulator with multiple equal-length segments as shown in FIG. 6D, or a series of electro-absorption modulators and phase modulators as shown in FIG. 6E. When the second electro-optical converter 202 has only a limited number of states (e.g., {1, 0, -1}, {1, -1}, {1, 0}), the second electro-optical converter 202 has the characteristics of low power consumption and high nonlinear tolerance.

[0063] If the response of the second electrical-to-optical converter 202 is assumed to be h(t), then the modulated local signal generated can be simply expressed as:

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[0065] The above describes the first electro-optical converter and the second electro-optical converter as examples. The following describes the second signal and the modulated local signal. For example, taking the first electro-optical converter shown in FIG. 3A as an example, the correlation signal B[n] of the specific signal to be measured and the modulated local signal E generated for different analog characteristics are as follows: L (t) can be given.

[0066] In some implementations, the analog characteristic is a frequency-independent IQ imbalance of a coherent transmitter, and the first signal is A[n]=A I [n]+jA Q [n], among which A I [n] and A Q [n] respectively represent signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B I 1 [n]=A I [n] and B Q 1 [n]=A Q [n], and B I 1 [n] and B Q 1 [n] are sequentially input to the second electrical-optical converter to form modulated local signals

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[0071] In some implementations, the first signal or the second signal may be quantized using at least one bit, and the quantized signal may be input to the second electrical-to-optical converter to obtain the modulated local signal.

[0072] For example, the target quantity to be monitored is the static IQ imbalance of an in-service coherent transmitter, such as IQ amplitude imbalance and IQ phase imbalance. Here, "static" means that the characteristic is a scalar quantity and is independent of frequency. The signal to be measured is A[n] = A I [n]+jA Q [n], of which A I [n] and A Q [n] respectively represent the signals loaded into the I path and Q path of the coherent transmitter. At this time, the correlation signal of the signal to be measured is B I 1 [n]=A I [n] and B Q 1 [n]=A Q [n], that is, B I 1 [n] and B Q 1 [n] is loaded into a second electrical-to-optical converter to produce a modulated local signal

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[0075] Also, for example, the monitored quantity is the static IQ imbalance of an in-service coherent transmitter, such as IQ amplitude imbalance and IQ phase imbalance. Here, "static" means that the characteristic is a scalar quantity and is independent of frequency. The signal to be measured is A[n] = A I [n]+jA Q [n], of which A I [n] and A Q [n] represent the signals loaded into the I and Q paths of the coherent transmitter, respectively. At this time, the correlation signal of the signal to be measured is B I 2 [n]=A I [n]+A I [n-1]+···+A I [nk] and B Q 2 [n]=A Q [n]+A Q [n-1]+···+A Q [nk], where k=1, 2, ..., K, can be selected. In this way, the measurement accuracy can be improved. Similarly, B I 2 [n] and B Q 2 [n] is loaded into a second electrical-to-optical converter to produce a modulated local signal

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[0078] Also, for example, the monitored quantity is the static IQ imbalance of an in-service coherent transmitter, such as IQ amplitude imbalance and IQ phase imbalance. Here, "static" means that the characteristic is a scalar quantity and is independent of frequency. The signal to be measured is A[n] = A I [n]+jA Q [n], of which A I [n] and A Q [n] respectively represent the signals loaded into the I path and Q path of the coherent transmitter. The correlation signal of the signal to be measured can also be a signal after quantizing the signal to be measured or the correlation signal of the signal to be measured using a limited number of bits, and the modulated local signal thus generated has only a limited number of states, which can reduce power consumption and hardware costs and reduce nonlinear effects.

[0079] For example, when the signal to be measured A[n] is a normal 64QAM communication signal, A I [n] and A Q The value of [n] has eight different states, {-7,-5,-3,-1,1,3,5,7}. At this time, the correlation signal B of the signal waiting to be measured I / Q 1 [n] has only two value states {-1, 1} and may be quantized by one bit, i.e., B I 1* [n]=sign(A I [n]) and B Q 1* [n]=sign(A Q [n]), where sign() is the sign function, i.e. sign(x)=1,if x>0 sign(x)=-1,if x<0 is.

[0080] Similarly, the correlation signal of the signal to be measured may further have only four value states {-3, -1, 1, 3} and may be quantized by two bits, i.e., B I 1* [n]=Quan(A I [n]) and B Q 1* [n]=Quan(A Q [n]), where Quan() is the quantization function, i.e., Quan(x)=-3, if x=-7 or -5 Quan(x)=-1, if x=-3 or -1 Quan(x)=1, if x=1 or 3 Quan(x)=3, if x=5 or 7 is.

[0081] For any other modulation formats, A[n] may all be quantized with a finite number of bits using the above-mentioned sign(x), Quan(x) or other similar functions to generate the correlation signal of the signal to be measured, where x is the above-mentioned A I / Q [n] may be used, and the above-mentioned B I / Q 1 [n] or B I / Q 2 [n] is also acceptable. For example, B I 2* [n]=sign(B I 2 [n])=sign(A I [n]+A I [n-1]+···+A I [nk]) and B Q 2* [n]=sign(B Q 2 [n])=sign(A Q [n]+A Q [n-1]+···+A Q [nk]) or B I 2* [n]=sign(A I [n])+sign(A I [n-1])++sign(A I [nk]) and BQ 2* [n]=sign(A Q [n])+sign(A Q [n-1])++sign(A Q [nk]), but a comprehensive listing is omitted here. For convenience, the modulated local signal generated based on the correlation signal of the signal to be measured after quantization processing is still

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[0083] In some implementations, the analog characteristic is an IQ skew of a coherent transmitter, and the first signal is A[n]=A I [n]+jA Q [n], among which A I [n] and A Q [n] respectively represent signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B I 3 [n]=A I [n]-A I [nm] and B Q 3 [n]=A Q [n]-A Q [nm], m=1, 2, ..., M, and B I 3 [n] and B Q 3 [n] are input to the second electrical-optical converter to form modulated local signals

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[0085] For example, the monitoring target quantity is the IQ skew of an in-service coherent transmitter. The signal to be measured is A[n]=A I [n]+jA Q[n], of which A I [n] and A Q [n] represent the signals loaded into the I and Q paths of the coherent transmitter, respectively. At this time, the correlation signal of the signal to be measured is B I 3 [n]=A I [n]-A I [nm] and B Q 3 [n]=A Q [n]-A Q [nm], where m=1, 2, ..., M, i.e., B I 3 [n] and B Q 3 [n] is loaded into a second electrical-to-optical converter to produce a modulated local signal

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[0087] For example, the monitoring target quantity is the IQ skew of an in-service coherent transmitter. The signal to be measured is A[n]=A I [n]+jA Q [n], of which A I [n] and A Q [n] respectively represent the signals loaded into the I path and Q path of the coherent transmitter. The correlation signal of the signal to be measured may be a signal after quantizing the signal to be measured or the above-mentioned correlation signal of the signal to be measured using a limited number of bits. The modulated local signal thus generated has only a limited number of states, which can reduce power consumption and hardware costs. For example, the correlation signal B of the signal to be measured can be quantized using the above-mentioned sign(x), Quan(x) or other similar functions using a finite number of bits. I / Q 3 Generate [n], x is A I / Q [n] may be used, and the above-mentioned BI / Q 3 It may be [n], and a detailed enumeration of specific quantization methods is omitted here. Similarly, the generated modulation local signal is

[0088] [Number] It can be expressed as, m is an even number, or

[0089] [Number] where m is an odd number. <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​4(q) [n] and B Q 4(q) [n] are input to the second electrical-optical converter to form modulated local signals

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[0093] For example, the monitoring target quantities include not only the static IQ imbalance (IQ amplitude imbalance, IQ phase imbalance, and IQ skew) of the in-service coherent transmitter, but also the frequency-correlated IQ imbalance of the in-service coherent transmitter, for example, the frequency response difference between the IQ paths. The signal to be measured is A[n]=A I [n]+jA Q [n], of which A I [n] and A Q [n] respectively represent the signals loaded into the I path and Q path of the coherent transmitter. At this time, the modulated local signal is

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[0098] Furthermore, for example, the monitoring target quantity includes not only the static IQ imbalance (IQ amplitude imbalance, IQ phase imbalance, and IQ skew) of the in-service coherent transmitter, but also the frequency-correlated IQ imbalance of the in-service coherent transmitter, for example, the difference in frequency response between the IQ paths. I [n]+jA Q [n], of which A I [n] and A Q [n] represent the signals loaded into the I and Q paths of the coherent transmitter, respectively. The correlation signal of the signal to be measured may be the signal to be measured or a signal after quantizing the correlation signal of the signal to be measured using a limited number of bits.

[0099] In some implementations, the analog characteristic is a frequency-independent difference between different segments or combinations of segments assigned according to bits in a transmitter, and the first signal is a signal A loaded into a segment or combination of segments assigned by the j-th bit. (j) [n], The second signal is B (j) 5 [n]=A (j) [n], and B (j)5 [n] are input to the second electrical-optical converter, respectively, to form the modulated local signal

[0100]

number

[0101]

number

[0102] For example, the monitored quantity is the static analog characteristic difference (amplitude) between different segments or entire segment combinations allocated according to bits in an in-service transmitter. (j) [n], which is the signal loaded into the segment or segment combination assigned by the j-th bit, and the value state is {-1,1}, {1,0}, or {-1,0}. At this time, the correlation signal of the monitoring signal is B (j) 5 [n]=A (j) [n], that is, B (j) 5 [n] is loaded into a second electrical-to-optical converter to produce a modulated local signal

[0103]

number

[0104] Also, for example, the monitoring target quantity is the static analog characteristic difference (amplitude) between different segments or entire segment combinations allocated according to bits in the transmitter under service. (j) [n], which is the signal loaded into the segment or segment combination assigned by the j-th bit, and the value state is {-1,1}, {1,0}, or {-1,0}. At this time, the correlation signal of the monitoring signal is B (j) 6 [n]=A (j) [n]+A (j) [n-1]+···+A (j) [nk], where k=1, 2, ..., K, can be selected to improve the measurement accuracy. Similarly, each B (j) 6 [n] is loaded into a second electrical-to-optical converter to produce a modulated local signal

[0105]

number

[0106] Also, for example, the monitoring target quantity is the static analog characteristic difference (amplitude) between different segments or entire segment combinations allocated according to bits in the transmitter under service. (j) [n], and is a signal loaded into a segment or a segment combination assigned by the j-th bit, and the value state is {-1,1}, {1,0}, or {-1,0}. In this case, the correlation signal of the signal to be measured may be a signal obtained by quantizing the signal to be measured or the correlation signal of the signal to be measured using a limited number of bits.

[0107] In some implementations, the analog characteristic is a skew difference between different segments or different combinations of segments assigned according to bits in a transmitter, and the first signal is a signal A loaded into a segment or combination of segments assigned by the j-th bit. (j) [n], The second signal is B (j) 7 [n]=A (j) [n]-A (j) [nm], and B (j) 7 [n] are input to the second electrical-optical converter to form modulated local signals

[0108]

number

[0109] For example, the monitoring target quantity is the static analog characteristic difference (skew) between different segments or entire segment combinations allocated according to bits in an in-service transmitter. (j) [n], which is the signal loaded into the segment or segment combination to be measured assigned by the j-th bit, and the value state is {-1,1}, {1,0} or {-1,0}. At this time, the correlation signal of the signal to be measured is B (j) 7 [n]=A (j) [n]-A (j) [nm], i.e., B (j) 7 [n] are sequentially loaded into the second electrical-optical converter, and the generated modulated local signal is

[0110]

number

[0111]

number

[0112] Also, for example, the monitored target quantity is the static analog characteristic difference (skew) between different segments or combinations of segments assigned according to bits in the in-service transmitter. The signal waiting for measurement can be represented as A (j) [n], which is a signal loaded into the segment or combination of segments waiting for measurement assigned by the j-th bit, and the value state is {-1, 1}, {1, 0} or {-1, 0}. At this time, the correlation signal of the signal waiting for measurement may be a signal obtained by quantizing the signal waiting for measurement or the correlation signal of the above-mentioned signal waiting for measurement using a limited number of bits.

[0113] In some embodiments, the analog characteristic is a difference related to frequency between different segments or different combinations of segments assigned according to bits in the transmitter, and the first signal is the signal A (j) [n] loaded into the segment or combination of segments assigned by the j-th bit, and the second signal is B (j) 8(q) =A (j) [n], and the B (j) 8(q) are respectively input into the second electro-optical converter to generate a modulation local signal

[0114] [Number] is generated, where 1 ≦ q ≦ Y, q is an integer, Y is an empirical value selected based on the analog characteristics of the transmitter waiting for measurement, τ is a unit delay smaller than T, or, when (q - 1)τ = mT + δ and 0 ≦ δ < T, the second signal is B (j) 8(q) =A(j) [nm], and B (j) 8(q) are input to the second electrical-optical converter, and are converted into modulated local signals

[0115]

number

[0116] For example, the monitored target quantity includes not only static analog characteristic differences (amplitude and phase imbalance, skew) between different segments or entire segment combinations allocated according to bits in a transmitter under service, but also frequency correlation differences, for example, frequency response differences between different segments or entire segment combinations allocated according to bits. (j) [n], and is a signal loaded into the segment or segment combination to be measured assigned by the j-th bit, and the value state is {-1,1}, {1,0}, or {-1,0}. At this time, the modulated local signal is

[0117]

number

[0118]

number

[0119]

number

[0120] Also, for example, the monitored target quantity includes not only static analog characteristic differences (amplitude and phase imbalance, skew) between different segments or entire segment combinations allocated according to bits in an in-service transmitter, but also frequency correlation differences, for example, frequency response differences between different segments or entire segment combinations allocated according to bits. (j) [n], and is a signal loaded into a segment or segment combination to be measured assigned by the j-th bit, and the value state is {-1,1}, {1,0}, or {-1,0}. In this case, the correlation signal of the signal to be measured may be a signal obtained by quantizing the signal to be measured or the correlation signal of the signal to be measured using a limited number of bits.

[0121] In some implementations, the analog characteristic is a difference between different segments or different segment combinations assigned according to bits across or within different polarization states in a dual-polarized transmitter; H and V respectively represent the H polarization state and the V polarization state of the dual polarization transmitter, and the second signals of the H path and the V path of the dual polarization transmitter are B H 9 [n] and B V 9 [n].

[0122] For example, the monitoring target is the analog characteristic difference (amplitude, skew or frequency response difference) between different segments or segment combinations assigned according to bits across or within different polarization states in a dual polarization transmitter under service, and the correlation signal B of the signal to be measured as described above can be obtained by the processing method described above. 1~8 [n] can be selected, and these signals can be unified to H / V 9 [n] and the corresponding modulated local signal E L-H / V 9 (t) can be generated, and detailed description thereof will be omitted here. In this, H and V represent the H polarization state and the V polarization state of the dual polarization transmitter, respectively, that is, B H 9 [n] and B V 9 Select [n].

[0123] In some implementations, the analog characteristic is an analog characteristic of the first electrical-to-optical converter under a specific symbol or a specific symbol sequence, and the first signal is represented as A[n] and the second signal B 10 [n] is a constant when it corresponds to the particular symbol, or 11 [n] is a constant when it corresponds to the central symbol of the particular symbol sequence, and the modulated local signal is a pulse signal.

[0124] For example, the monitoring target quantity is the analog characteristic of the first electrical-optical converter under a specific symbol or a specific symbol sequence while in service (for example, for a coherent transmitter, any one of its independent I or Q paths is considered, for a dual-polarization intensity modulation transmitter, any one of its polarization state paths is considered, and for a dual-polarization coherent transmitter, any one of its independent I or Q paths in any one of its polarization states is considered). For example, suppose that the signal to be measured A[n] at this time is a PAM8 signal, and each symbol in A[n] is a random one of {-7, -5, -3, -1, 1, 3, 5, 7}. In this case, by selecting an appropriate correlation signal of the signal to be measured, it is possible to make the generated modulated local signal a single pulse signal. For example, when the monitoring target quantity is the analog characteristic of the first electrical-optical converter when the input symbol is [-3], the signal to be measured is B 10 [n] can be selected, specifically, B 10 [n]=C,if A[n]=-3 B 10 [n]=0, if A[n]≠-3 In this case, C is a constant, which may be 1 or another non-zero constant. Since any other specific symbols can be inferred based on this, a comprehensive list is omitted here. The generated modulated local signal is E L 10 It is marked as (t).

[0125] For example, the monitoring target quantity is the analog characteristic when the input symbol sequence of the first electro-optical converter is

[0715] , and the measurement waiting signal is B 11 [n] can be selected, specifically, B 11 [n]=C,if A[n-1]=7 and A[n]=1 and A[n+1]=5 B 11 [n]=0,if A[n-1]≠7 or A[n]≠1 or A[n+1]≠5 There is.

[0126] Similarly, C is a constant, which may be 1 or another non-zero constant. Other specific symbol sequences of length 3 or longer can be inferred based on this, so a comprehensive list is omitted here. The generated modulated local signal is E L 11 It is marked as (t).

[0127] In addition, the correlation signal B of all signals waiting to be measured 1~11 [n] does not need to be loaded in real time, that is, it is turned on after a predetermined time (period) T1 and lasts for a time T2, that is,

[0128]

number

[0129] In this way, the overall monitoring power consumption can be reduced.

[0130] Also, for example, the monitoring target quantity is the above-mentioned various target quantities to be measured in the transmitter under pre-service, and the signal to be measured may be a specially designed test signal, and the value state is not limited. For example, when testing the analog characteristics of the I path of a coherent transmitter, Q [n]=0, and for a modulator having a structure in which segments are cascaded, when testing the analog characteristics of the segment or segment combination assigned by the z-th bit, A (j) [n]=0 and j≠z, which completely avoids interference from non-measured segments or segment combinations. Also, the correlation signal of the signal to be measured is still the above-mentioned signal B 1~11 [n] can be adopted to select, and an exhaustive enumeration is omitted here.

[0131] In some embodiments, the analog characteristics are the static and dynamic analog characteristics of each segment in a transmitter having a structure in which a plurality of segments of modulators are cascaded, and the first signal of the segment waiting for measurement is A (s) [n], and the first signal of the non-segment waiting for measurement is A (w) [n]=0, w≠s, The second signal is B (s) 12(q) =A (s) [n], and the B (s) 12(q) are respectively input into the second electro-optic converter to generate a modulation local signal

[0132]

Number

[0133]

Number

[0134] For example, the monitoring target is the static and dynamic analog characteristics of each segment in a transmitter having a structure in which a plurality of segments of modulators are cascaded, and all segments can be tested one by one at the pre-service stage. For example, when the segment to be measured is the s-th segment, the test signal can be expressed as A (w) [n]=0, w≠s, that is, all other non-segment waiting for measurement transmit all-zero signals or are off and not working, and the test signal A on the segment waiting for measurement (s)[n] is an arbitrary random signal with good autocorrelation properties. Then, the modulated local signal is

[0135]

number

[0136]

number

[0137]

number

[0138] The second signal and the modulated local signal have been described above as examples, and the correlation processor will be described below with reference to FIG. 2 again.

[0139] As shown in FIG. 2, the correlation processor 203 uses low-speed optical-electrical devices and electrical devices to convert the optical signal to be measured E output from the first electrical-optical converter 201 into s (t) and the modulated local signal E output by the second electrical-optical converter 202 L(t) is subjected to correlation processing, and the correlation amount of these two signals is obtained as follows:

[0140]

number

[0141] There are several ways to perform correlation processing based on parallel modulation, and specific implementation methods for different target monitoring quantities will be explained below using the first electro-optical converter in Figures 3, 4 and 5 and the second electro-optical converter in Figure 6 as examples. When the monitoring target quantity is the analog characteristics of the in-service transmitter, the correlator can be implemented in the following ways:

[0142] In some implementations, the first electrical-to-optical converter is a coherent transmitter.

[0143] 7 is a diagram showing correlation processing in an embodiment of the present invention, illustrating the case of correlation processing for monitoring IQ imbalance of a coherent transmitter when the first electrical-optical converter is one coherent transmitter. As shown in FIG. 7, a portion of the DC light is transmitted to the second electrical-optical converter before the modulator. The correlation processor is realized based on an optical-electrical multiplier and an electrical averaging unit.

[0144] As shown in Figure 7, the optical-electrical multiplier includes a selectable phase shifter (i.e., φ is optional), a 90° optical mixer, and a balanced photodetector (BPD), and the electrical averaging unit includes a low-pass filter and a low-speed ADC, and the electrical averaging operation can be realized in the analog domain or the digital domain. When the electrical averaging operation is realized in the analog domain, the low-speed ADC monitors the voltage average value.<V1(t)> and<V2(t)> When the electrical averaging operation is realized in the digital domain, the low-speed ADC outputs the monitoring voltage signals V1(t) and V2(t), and then in the manner of digital averaging<V1(t)> and<V2(t)> Get.

[0145] The output optical signal of the coherent transmitter is E S (t)=E S-I (t)+jE S-Q (t), and the output signal of the second optical-electrical converter is denoted as E L (t) and the phase difference between them is denoted as φ. After passing through one ideal 90° optical mixer, the output optical signal can be expressed as:

[0146]

number

[0147] Then the output current of the balanced photodetector (BPD) can be expressed as:

[0148]

number

[0149] Among them, R BPD represents the response of the balanced photodetector, and φ represents a constant phase.

[0150]

number

[0151] It should be noted that the embodiment shown in FIG. 7 is merely an example, and the specific details of each unit may vary.

[0152] 8 shows possible output ports of the first electro-optical converter in an embodiment of the present invention. For example, the output signal of the first electro-optical converter is the other path output signal I-jQ of the 2*2 multi-mode interference coupler (MMI) in FIG. 7, but it can also be the normal output signal I+jQ of the transmitter shown in FIG. 8 or the output of another monitoring path.

[0153] 9A to 9D are diagrams illustrating an opto-electrical multiplier according to an embodiment of the present invention. The opto-electrical multiplier may be realized in several ways, such as using a selectable phase shifter, a 90-degree hybrid, and two balanced photodetectors as shown in FIG. 9A, using a phase shifter, a 180-degree hybrid, and two single opto-electrical detectors as shown in FIG. 9B, using a selectable phase shifter, a 120-degree hybrid, and three single opto-electrical detectors as shown in FIG. 9C, or using a phase shifter, a coupler, and a single opto-electrical detector as shown in FIG. 9D.

[0154] 10A and 10B are diagrams illustrating an electrical averaging unit with square wave multiplication and frequency shifting functions added in an embodiment of the present invention. The electrical averaging operation can be implemented in the analog or digital domain. For example, it can be implemented using a low-pass filter or by performing mathematical averaging on the signal sampled by a low-speed ADC. Furthermore, square wave multiplication and frequency shifting can be implemented by simultaneously multiplying the correlation signal and product signal of the signal to be measured by a 125 MHz square wave. This shifts the correlation value from DC to the 125 MHz frequency, thereby avoiding 1 / f noise near DC. As shown in FIG. 10A, the multiplication with the product signal can be performed in the analog domain, or as shown in FIG. 10B, it can be performed in the digital domain; however, this is not a limitation of the embodiments of the present invention.

[0155] In some implementations, the first electrical-optical converter is a segment or a combination of segments that are assigned according to bits in the coherent transmitter. The second electrical-optical converter is an independent electrical-optical converter as shown in Figure 6, and the implementation of correlation processing can still adopt the embodiment shown in Figure 7.

[0156] 11A and 11B are diagrams showing the first and second electrical-optical converters in an embodiment of the present invention, and illustrate the relationship between the first and second electrical-optical converters when the first electrical-optical converter is a certain segment (as shown in FIG. 11A) or a segment combination (as shown in FIG. 11B) allocated according to bits in a coherent transmitter. At this time, the implementation of the optical-electrical multiplier can be seen in FIG. 9. The correlation quantity obtained is V1 j [q] and V2 j It is written as [q], where j represents the segment or segment combination assigned by the j-th bit to be measured. For all differently modulated local signals, this method is adopted to obtain the correlation amount.

[0157] In some implementations, the first electro-optical converter is an MZM intensity modulator or a segment or combination of segments allocated according to bits therein. The second electro-optical converter is an independent electro-optical converter as shown in FIG.

[0158] Figure 12 shows a first electro-optical converter and a second electro-optical converter in an embodiment of the present invention, where the first electro-optical converter is an MZM intensity modulator or a certain segment or segment combination assigned according to bits therein, and the second electro-optical converter is an independent electro-optical converter. As shown in Figure 12, the opto-electrical multiplier is configured with a single opto-electrical detector. Correlation quantities can be obtained in this manner for all different modulated local signals. Wherein, j represents the segment or segment combination assigned by the jth bit to be measured.

[0159] In some implementations, the first electrical-optical converter is a dual-polarized transmitter, and the second electrical-optical converter is an independent electrical-optical converter as shown in Figure 6. Analog characteristics of the entire different polarization states can be monitored based on the above-mentioned embodiments, and when the first electrical-optical converter is a different segment or segment combination assigned according to bits within each polarization state of the dual-polarized transmitter, and the second electrical-optical converter is an independent electrical-optical converter as shown in Figure 6, each polarization state can be monitored based on the above-mentioned embodiments. Correlation quantities are obtained for different modulated local signals, and a comprehensive list is omitted here.

[0160] When the monitoring target quantity is the analog characteristics of the transmitter in pre-service, the above-mentioned implementation method can be adopted to perform correlation processing on the modulated local signal and the signal to be measured. The present invention is not limited to the above implementation method, and the following method may also be adopted.

[0161] 13 is a diagram showing a first electrical-optical converter and a second electrical-optical converter in an embodiment of the present invention. The first electrical-optical converter is any given segment or combination of segments in a coherent transmitter, and the second electrical-optical converter is any given segment or combination of segments or the entire parallel path in parallel with the first electrical-optical converter in the coherent transmitter. Unlike the conventional coherent transmitter configuration, the phase difference between the I path and the Q path is 0 degrees in this case, which allows the correlation processing of the first electrical-optical converter and the second electrical-optical converter shown in FIG. 2 to be realized. The optical-electrical multiplier is composed of only one single optical-electrical detector, and the correlation quantity V is calculated by electrical averaging. j [q] can be obtained. For different modulated local signals, such a method can be used to obtain the correlation amount, and a comprehensive list will be omitted here.

[0162] The correlation processor has been described above as an example, and the analog characteristic estimator 204 will now be described with reference to Fig. 2 again. The analog characteristic estimator 204 can estimate the corresponding target monitoring quantities based on all the correlation quantities described above.

[0163] for example, i)

[0164]

number

[0165]

number

[0166]

number

[0167]

number

[0168] ii)

[0169]

number

[0170]

number

[0171]

number

[0172] iii)

[0173]

number

[0174]

number

[0175]

number

[0176] Also,

[0177]

number

[0178]

number

[0179]

number

[0180]

number

[0181] Correlation quantities obtained for correlation signals of signals to be measured obtained after quantization using a limited number of bits

[0182]

number

[0183]

number

[0184] Also, V1 9-H [q], V2 9-H [q], V1 9-V [q] and V2 9-V [q] or V 9-H [q] and V 9-V Similarly, for [q], the imbalance between corresponding polarization states or the imbalance between different segments within a polarization state can be calculated by referring to the above contents.

[0185] Also,

[0186]

number

[0187] Also,

[0188]

number

[0189] Parallel modulation has been described above by way of example using FIG. 2, and serial modulation will be described below.

[0190] In some embodiments, the first electrical-optical converter and the second electrical-optical converter are connected in series, the first electrical-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, the second electrical-optical converter generates the modulated local signal based on the optical signal to be measured and the second signal, the modulated local signal is input to an optical-electrical converter to obtain an electrical signal, and the electrical signal is electrically averaged to generate the at least one correlation quantity.

[0191] 14 is a diagram showing a serial modulation correlation processing based transmitter analog characteristic monitoring device in an embodiment of the present invention. As shown in FIG. 14, the device may include: First electrical-optical converter 1401: the optical transmitter itself or only a part of the optical transmitter, whose analog characteristics are the target quantity to be monitored, generates an optical signal to be measured; A second electrical-optical converter 1402 generates an optical product signal according to the correlation signal of the signal to be measured, and realizes the multiplication operation of the optical signal to be measured and the correlation signal of the signal to be measured in the optical domain; Optical-electrical converter 1403: converts optical product signals into electrical signals; An electrical averaging unit 1404: performs electrical averaging on the electrical signal output by the optical-electrical converter to obtain the correlation amount between the signal to be measured and the correlation signal of the signal to be measured; and Analog characteristic estimator 1405: Estimates the analog characteristic of the first electrical-optical converter based on the signal correlation amount.

[0192] Although FIG. 14 exemplarily illustrates structures for implementing monitoring of the analog characteristics of an optical transmitter, the present invention is not limited to these structures. Furthermore, appropriate modifications can be made to these structures, and all of the implementation methods of these modifications are included in the scope of the embodiments of the present invention.

[0193] As shown in Fig. 14, the first electro-optical converter 1401 generates an optical signal to be measured corresponding to the signal to be measured A[n] through modulation, and inputs it to the second electro-optical converter 1402. The first electro-optical converter 1401 may be a complete optical transmitter, or may be only a part of an optical transmitter. Note that the embodiments of the present invention are not limited to the type and structure of the first electro-optical converter 1401. For example, it may have the variations shown in Figs. 3, 4, and 5, and may even be a directly modulated laser.

[0194] FIG. 15 is a diagram illustrating a first electrical-optical converter in an embodiment of the present invention. As shown in FIG. 15, the first electrical-optical converter may be a directly modulated laser (DML or EML).

[0195] If the response of the first electrical-optical converter is g(t), the optical signal to be measured that is generated is

[0196]

number

[0197] As shown in Figure 14, the second electro-optical converter 1402 loads the correlation signal B[n] of the signal to be measured into the optical signal to be measured to generate an optical product signal, that is, the multiplication operation of the optical signal to be measured and the correlation signal of the signal to be measured is completed directly in the optical domain through serial modulation. Serial modulation is a natural multiplication operation. The optical product signal can essentially still be regarded as a modulated local signal.

[0198] The type and structure of the second electro-optical converter 1402 may also have multiple forms, such as the variant shown in Figure 6. In addition, according to different monitored target quantities, the correlation signal B[n] of the signal to be measured may also have multiple different options to generate different optical product signals, but this is not limited to this embodiment of the present invention.

[0199] In addition, all the monitoring target quantities mentioned in the parallel modulation correlation processing and the correlation signal B 1~12 [n] is also applicable here. The difference is that the output signal of the second electro-optical converter is now an optical product signal

[0200]

number

[0201] As shown in FIG. 14, the optical-electrical converter 1403 converts the optical product signal into an electrical signal, and there are a number of serial modulation and optical-electrical conversion (detection) methods according to different monitoring target quantities.

[0202] 16 is a diagram illustrating serial-based modulation and coherent detection in an embodiment of the present invention. As shown in FIG. 16, the optical-to-electrical converter includes one selectable phase shifter (optional), a 90-degree mixer, and a balanced photodetector to convert the optical domain product signal into an electrical signal. Note that although FIG. 16 shows an exemplary implementation, the optical-to-electrical converter may have the modifications shown in FIG. 9.

[0203] Analog characteristic monitoring can be performed based on the above embodiments when the monitored target quantity is the analog characteristic difference between each segment or segment combination within a transmitter, or when the monitored target quantity is the analog characteristic difference (amplitude, skew, or frequency response difference) across different polarization states or between each segment or segment combination in different polarization states within a dual-polarized transmitter, or when the monitored target quantity is the analog characteristic under a specific symbol or symbol sequence of the first electrical-to-optical converter.

[0204] 17 is a diagram showing another transmitter analog characteristic monitoring in an embodiment of the present invention. When the first electrical-to-optical converter is a directly modulated laser, it can be directly monitored as shown in FIG.

[0205] Although the above describes an optical transmitter analog characteristic monitoring method and some hardware structures for implementing the method as examples, the present invention is not limited to these. The monitoring method may further include other steps or processes, and the specific content of these steps or processes can be found in the prior art. Furthermore, although the above describes a hardware structure for implementing the monitoring method as an example, the present invention is not limited to these hardware structures, and appropriate modifications can be made to these structures, and all of these modified implementation methods are within the scope of the embodiments of the present invention.

[0206] In an embodiment of the present invention, a first electrical-optical converter (the transmitter itself or a part of the transmitter) generates an optical signal to be measured, a second electrical-optical converter generates different modulated local signals based on differences in the monitored target quantities, and a correlation processor uses low-speed opto-electrical devices and electrical devices to complete the correlation operation between the optical signal to be measured and the modulated local signal, and calculates the analog characteristics of the transmitter based on the correlation quantity between the optical signal to be measured and the modulated local signal.

[0207] In the embodiment of the present invention, the correlation operation may be performed in two schemes: parallel and serial. In the parallel scheme, the optical signal to be measured and the modulated local signal are added in the optical domain, and then multiplied and averaged in the electrical domain using an optical-to-electrical converter. In the serial scheme, the second electro-optical modulator directly modulates the optical signal to be measured, and the multiplication of the optical signal to be measured and the correlation signal of the optical signal to be measured is performed in the optical domain, and then the averaging is performed in the electrical domain.

[0208] In the embodiment of the present invention, the realization of the optical-electrical converter still has several ways, such as 90° hybrid coherent receiver, 180° hybrid and balanced optical detector, 120° hybrid and single optical-electrical detector, etc. Multiplication in the optical domain can be realized by serial modulation.

[0209] In an embodiment of the present invention, when the monitored target quantity is an imbalance in static analog characteristics (amplitude, phase, and skew), the generated modulated local signal may be a single signal, and when the monitored target quantity is a difference in analog characteristics related to frequency, the generated modulated local signal may be a signal including multiple different delays.

[0210] In an embodiment of the present invention, the second electrical-to-optical converter has the advantage that when there are only a finite number of states, the power consumption and hardware costs of the entire monitoring device can be reduced.

[0211] The above-described embodiments are provided to exemplify the present invention, but the present invention is not limited to these, and appropriate modifications can be made based on the above-described embodiments. For example, each of the above-described embodiments may be used alone, or a plurality of the above-described embodiments may be used in combination.

[0212] As can be seen from the above-described embodiment, the correlation between the optical signal to be measured and the modulated local signal is used to extract analog characteristic information of the optical transmitter, which reduces the required hardware cost significantly compared to that of a conventional broadband receiver and eliminates the need for complex DSP processing, thereby enabling a significant reduction in power consumption.

[0213] <Example of the second aspect> In the embodiment of the present invention, a monitoring device exclusive to an optical transmitter analog is provided, and the description of the same contents as in the embodiment of the first aspect will be omitted here.

[0214] FIG. 18 is a diagram showing an optical transmitter analog characteristic monitoring device according to an embodiment of the present invention. As shown in FIG. 18, an optical transmitter analog characteristic monitoring device 1800 includes: A first input unit 1801: inputs a first signal into a first electrical-optical converter to obtain an optical signal to be measured; A second input unit 1802: inputs a second signal into a second electro-optical converter to obtain a modulated local signal, where the second signal is determined according to the first signal and the analog characteristics of the first electro-optical converter being monitored; A correlation unit 1803 performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and An estimation unit 1804: estimates the analog characteristics of the first electrical-optical converter based on the correlation amount.

[0215] In some embodiments, the correlation quantity represents a value at a first time of an impulse response when the first electrical-to-optical converter and the second electrical-to-optical converter are cascaded, and the first time depends on the relative delay between the first signal and the second signal.

[0216] In some embodiments, when the transmitter transmits at least two superimposed signals, the transmitter performs at least one monitoring for each signal to obtain at least two correlation quantities, and estimates the analog characteristics of the first electrical-optical converter based on the at least two correlation quantities.

[0217] In some embodiments, the analog characteristic is a frequency-independent IQ imbalance of a coherent transmitter, and the first signal is A[n]=A I [n]+jA Q [n], among which A I [n] and A Q [n] represent signals loaded onto the I and Q paths of the coherent transmitter, respectively; The second signal is B I 1 [n]=A I [n] and B Q 1 [n]=A Q [n], and B I 1 [n] and B Q 1 [n] are input to the second electrical-optical converter to form modulated local signals

[0218]

number

[0219]

number

[0220]

number

[0221]

number

[0222] In some embodiments, the analog characteristic is an IQ skew of a coherent transmitter, and the first signal is A[n]=A I [n]+jA Q [n], among which A I [n] and A Q [n] represent signals loaded onto the I and Q paths of the coherent transmitter, respectively; The second signal is B I 3 [n]=A I [n]-A I [nm] and B Q 3 [n]=A Q [n]-A Q [nm], m=1, 2, ..., M, and B I 3 [n] and B Q 3 [n] are input to the second electrical-optical converter to form modulated local signals

[0223]

number

[0224] In some embodiments, the analog characteristic is an IQ imbalance related to the frequency of a coherent transmitter, and the first signal is A[n]=A I [n]+jA Q [n], where A I [n] and A Q [n] respectively represent the signals loaded on the I path and the Q path of the coherent transmitter, The second signal is B I / Q 4(q) [n]=A I / Q [n], and B I 4(q) [n] and B Q <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In some embodiments, the analog characteristic is a frequency-independent difference between different segments or different segment combinations assigned according to bits in a transmitter, and the first signal is a signal A loaded into a segment or segment combination assigned by the j-th bit. (j) [n], The second signal is B (j) 5 [n]=A (j) [n], and B (j) 5 [n] are input to the second electrical-optical converter to form modulated local signals

[0228]

number

[0229]

number

[0230] In some embodiments, the analog characteristic is a skew difference between different segments or different combinations of segments assigned according to bits in a transmitter, and the first signal is a signal A loaded into a segment or combination of segments assigned by the j-th bit. (j) [n], The second signal is B (j) 7 [n]=A (j) [n]-A (j) [nm], and B (j)7 [n] is input to the second electro-optical converter respectively to generate a modulation local signal

[0231]

Number

[0232]

Number

[0233]

Number

[0234] In some embodiments, the analog characteristic is a difference between different segments or different segment combinations assigned according to bits across or within different polarization states in a dual polarization transmitter, where H and V represent the H polarization state and the V polarization state of the dual polarization transmitter, respectively, and the second signals of the H path and the V path of the dual polarization transmitter are B H 9 [n] and B V 9 [n].

[0235] In some embodiments, the analog characteristic is an analog characteristic of the first electrical-to-optical converter under a particular symbol or a particular symbol sequence, the first signal is denoted as A[n], and the second signal B 10 [n] is a constant when it corresponds to the particular symbol, or 11 [n] is a constant when it corresponds to the central symbol of the particular symbol sequence, and the modulated local signal is a pulse signal.

[0236] In some embodiments, the analog characteristics are static and dynamic analog characteristics of each segment in a transmitter having a structure in which a plurality of stages (segments) of modulators are cascaded, and the first signal of the segment to be measured is A (s) [n], and the first signal of the non-measurement waiting segment is A (w) [n]=0, w≠s, The second signal is B (s) 12(q) =A (s) [n], and B (s) 12(q) are input to the second electrical-optical converter, and are converted into modulated local signals

[0237]

number

[0238]

Number

[0239] In some embodiments, the apparatus further includes the following, namely, A quantization unit: performs quantization on the first signal or the second signal using at least one bit, and inputs the quantized signal into the second electro - optical converter to obtain the modulation local signal.

[0240] In some embodiments, the first electro - optical converter is a transmitter, or a modulation unit of a part of the transmitter, or a direct modulation laser.

[0241] In some embodiments, the second electro - optical converter outputs a limited number of states.

[0242] In some embodiments, the first electro - optical converter and the second electro - optical converter are in parallel. The first electro - optical converter generates the optical signal waiting for measurement based on the optical carrier and the first signal, the second electro - optical converter generates the modulation local signal based on the optical carrier and the second signal. The optical signal waiting for measurement and the modulation local signal are respectively input into an optoelectronic multiplier to obtain a product electrical signal, and the product electrical signal is electrically averaged to generate the at least one correlation quantity.

[0243] In some embodiments, the first electrical-optical converter and the second electrical-optical converter are connected in series, the first electrical-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, the second electrical-optical converter generates the modulated local signal based on the optical signal to be measured and the second signal, the modulated local signal is input to an optical-electrical converter to obtain an electrical signal, and the electrical signal is electrically averaged to generate the at least one correlation quantity.

[0244] Although only the components or modules according to the present invention have been described above, the present invention is not limited to these. The optical transmitter analog characteristic monitoring device 1800 may further include other components or modules, and the specific contents of these components or modules can be found in the related art.

[0245] For convenience, Fig. 18 shows the connection relationships or signal directions between each component or module, but as will be understood by those skilled in the art, various technologies such as bus connection may be adopted. Each of the above-described components or modules may be realized by hardware such as a processor, a memory, etc., but the embodiments of the present invention are not limited thereto.

[0246] The above-described embodiments are provided to exemplify the present invention, but the present invention is not limited to these, and appropriate modifications can be made based on the above-described embodiments. For example, each of the above-described embodiments may be used alone, or a plurality of the above-described embodiments may be used in combination.

[0247] As can be seen from the above-described embodiment, the correlation between the optical signal to be measured and the modulated local signal is used to extract analog characteristic information of the optical transmitter, which reduces the required hardware cost significantly compared to that of a conventional broadband receiver and eliminates the need for complex DSP processing, thereby enabling a significant reduction in power consumption.

[0248] <Example of the third aspect> In an embodiment of the present invention, an electronic device is provided, which includes the optical transmitter analog characteristic monitoring device 1800 described in the embodiment of the second aspect, the contents of which are incorporated herein by reference. The electronic device may be, for example, a computer, a server, a workstation, a desktop PC, a smartphone, etc., but the embodiment of the present invention is not limited thereto.

[0249] 19 is a diagram illustrating an electronic device according to an embodiment of the present invention. As shown in FIG. 19, the electronic device 1900 may include a processor (e.g., a central processing unit (CPU)) 1910 and a memory 1920, the memory 1920 being connected to the central processing unit 1910. The memory 1920 can store various data and can also store a program 1921 for information processing, and can execute the program 1921 under the control of the processor 1910.

[0250] In some embodiments, the functionality of the optical transmitter analog characteristic monitoring device 1800 may be integrated into the processor 1910, where the processor 1910 is configured to implement the optical transmitter analog characteristic monitoring method described in the embodiments of the first aspect.

[0251] In some embodiments, the optical transmitter analog characteristic monitoring device 1800 may be located separately from the processor 1910, for example, the optical transmitter analog characteristic monitoring device 1800 may be configured as a chip connected to the processor 1910, and the functions of the optical transmitter analog characteristic monitoring device 1800 may be realized under the control of the processor 1910.

[0252] For example, the processor 1910 is configured to perform the following control: input a first signal to a first electro-optical converter to obtain an optical signal to be measured; input a second signal to a second electro-optical converter to obtain a modulated local signal, in which the second signal is determined based on the first signal and the analog characteristic of the first electro-optical converter to be monitored; perform correlation processing on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and estimate the analog characteristic of the first electro-optical converter based on the correlation quantity.

[0253] 19, the electronic device 1900 may further include an input / output (I / O) device 1930, a display 1940, etc., among which the functions of the above-mentioned components are similar to those of the prior art, and therefore detailed description thereof will be omitted here. Note that the electronic device 1900 does not need to include all the components shown in FIG. 19. The electronic device 1900 may further include components not shown in FIG. 19, and for this, reference can be made to the related art.

[0254] An embodiment of the present invention further provides an optical transmitter, which includes a first electrical-optical converter and a second electrical-optical converter, characterized in that a first signal is input to the first electrical-optical converter to obtain an optical signal to be measured, and a second signal is input to the second electrical-optical converter to obtain a modulated local signal, wherein the second signal is determined based on the first signal and the analog characteristic to be monitored of the first electrical-optical converter.

[0255] The optical transmitter further includes a monitoring device that performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity, and estimates the analog characteristics of the first electrical-optical converter based on the correlation quantity.

[0256] An embodiment of the present invention further provides a computer-readable program, which, when executed in an electronic device, causes a computer to execute the optical transmitter analog characteristic monitoring method described in the embodiment of the first aspect in the electronic device.

[0257] In a further embodiment of the present invention, a storage medium is provided having stored thereon a computer-readable program, wherein the computer-readable program causes a computer to execute the optical transmitter analog characteristic monitoring method described in the embodiment of the first aspect in an electronic device.

[0258] The above-described devices and methods may be realized by software or hardware, or by a combination of hardware and software. The present invention further relates to a computer-readable program as described below, which, when executed by a logic component, causes the logic component to realize the above-described devices or components, or to perform each of the above-described methods or steps. The logic component may be, for example, an FPGA (Field Programmable Gate Array), a microprocessor, or a processing unit used in a computer. The present invention also relates to a storage medium, such as a hard disk, magnetic disk, optical hard disk, DVD, or flash memory, that stores the above-described program.

[0259] Furthermore, one or more combinations of the functional blocks illustrated in the figures and / or one or more combinations of the functional blocks may be implemented as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic component, a discrete gate or transistor logic component, a discrete hardware assembly, or any other suitable combination for performing the functions described herein. Also, one or more combinations of the functional blocks illustrated in the figures and / or one or more combinations of the functional blocks may be further implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors communicatively coupled with a DSP, or any other configuration.

[0260] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and any modifications to the present invention that do not depart from the spirit of the present invention fall within the technical scope of the present invention.

[0261] Furthermore, the following additional notes are disclosed regarding the above-described embodiments.

[0262] (Appendix 1) An optical transmitter analog characteristic monitoring device, a first input unit for inputting a first signal into a first electrical-optical converter to obtain an optical signal to be measured; a second input unit for inputting a second signal to a second electro-optical converter to obtain a modulated local signal, the second signal being determined based on the first signal and a monitored analog characteristic of the first electro-optical converter; a correlation unit that performs correlation processing on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and an estimation unit for estimating an analog characteristic of the first electrical-optical converter based on the correlation amount.

[0263] (Appendix 2) 10. The apparatus of claim 1, The correlation quantity represents a value of an impulse response at a first time when the first electro-optical converter and the second electro-optical converter are cascaded, and the first time depends on a relative delay between the first signal and the second signal.

[0264] (Appendix 3) 10. The apparatus of claim 1, For at least two superimposed signals transmitted by a transmitter, performing at least one monitoring for each signal to obtain at least two correlation quantities, and estimating the analog characteristics of the first electrical-optical converter based on the at least two correlation quantities.

[0265] (Appendix 4) 10. The apparatus of claim 1, the analog characteristic is the frequency-independent IQ imbalance of a coherent transmitter; The first signal is A[n]=A I [n]+jA Q [n] and A I [n] and A Q [n] respectively represent signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B I 1 [n]=A I [n] and B Q 1 [n]=A Q [n], and B I 1 [n] and B Q 1 [n] are sequentially input to the second electrical-optical converter, respectively, to form a modulated local signal

[0266]

number

[0267]

number

[0268]

number

[0269]

number

[0270] (Appendix 5) 10. The apparatus of claim 1, the analog characteristic is an IQ deviation of a coherent transmitter; The first signal is A[n]=A I [n]+jA Q [n] and A I [n] and A Q [n] respectively represent signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B I 3 [n]=A I [n]-A I [nm] and B Q 3 [n]=A Q [n]-A Q [nm], m=1, 2, ..., M, and B I 3 [n] and B Q 3 [n] are sequentially input to the second electrical-optical converter, respectively, to form a modulated local signal

[0271]

number

[0272] (Appendix 6) 10. The apparatus of claim 1, the analog characteristic is a frequency-related IQ imbalance of a coherent transmitter; The first signal is A[n]=A I [n]+jA Q [n] and A I [n] and A Q [n] respectively represent signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B I / Q 4(q) [n]=A I / Q [n], and B I 4(q) [n] and B Q 4(q) [n] are sequentially input to the second electrical-optical converter, respectively, to form a modulated local signal

[0273] [Number] is generated, where 1 ≤ q ≤ Y, q is an integer, Y is an empirical value selected based on the analog characteristics of the transmitter waiting to be measured, τ is a unit delay smaller than T, or, when (q - 1)τ = mT + δ and 0 ≤ δ < T, the second signal is B I / Q 4(q) [n] = A I / Q [n - m], and the B I 4(q) [n] and B Q 4(q) [n] are sequentially input into the second electro - optical converter respectively, so as to generate a modulation local signal

[0274] [Number] is generated.

[0275] (Appendix 7) The device according to Appendix 1, [[ID=३७]]where the analog characteristics are frequency - independent differences between different stages or different combinations of stages assigned according to bits within the transmitter, the first signal is the signal A (j) [n] loaded into the stage or combination of stages assigned by the j - th bit, the second signal is B (j) 5 [n] = A <০০০০৫১৯>[n], and the B (j) 5 [n] are sequentially input into the second electro - optical converter respectively, so as to generate a modulation local signal

[0276] [[ID=5५]] [Number] <00০1986>is generated, or, the second signal is B (j) 6 [n] = A (j) [n] + A(j) [n-1]+···+A (j) [nk], where k=1, 2, ..., K, and B (j) 6 [n] are sequentially input to the second electrical-optical converter, respectively, to form a modulated local signal

[0277]

number

[0278] (Appendix 8) 10. The apparatus of claim 1, the analog characteristic is a deviation difference between different stages or different stage combinations allocated according to bits in the transmitter; The first signal is signal A that is loaded into the stage or stage combination assigned by the j-th bit. (j) [n], The second signal is B (j) 7 [n]=A (j) [n]-A (j) [nm], and B (j) 7 [n] are sequentially input to the second electrical-optical converter, respectively, to form a modulated local signal

[0279]

number

[0280] (Appendix 9) 10. The apparatus of claim 1, the analog characteristic being a frequency-related difference between different stages or stage combinations allocated according to bits in the transmitter; The first signal is signal A that is loaded into the stage or stage combination assigned by the j-th bit. (j) [n], The second signal is B (j) 8(q) =A (j)is [n], and the said B (j) 8(q) are sequentially input into the said second electro-optical converter respectively, so as to generate a modulation local signal

[0281] [Number] is generated, 1 ≤ q ≤ Y, q is an integer, Y is an empirical value selected based on the analog characteristics of the transmitter waiting for measurement, τ is a unit delay smaller than T, or, when (q - 1)τ = mT + δ and 0 ≤ δ < T, the said second signal is B (j) 8(q) = A (j) [n - m], and the said B (j) 8(q) are sequentially input into the said second electro-optical converter respectively, so as to generate a modulation local signal

[0282] [Number] is generated.

[0283] <H (Appendix 10) The device according to Appendix 1, where the said analog characteristics are the differences between different polarization states or within different polarization states in a dual-polarization transmitter, between different stages or different stage combinations assigned according to bits, where H and V respectively represent the H polarization state and V polarization state of the dual-polarization transmitter, the second signals of the H path and V path of the said dual-polarization transmitter are respectively B H 9 [n] and B V 9 [n].

[0284] (Appendix 11) The device according to Appendix 1, where the said analog characteristics are the analog characteristics of the said first electro-optical converter under a specific symbol or a specific symbol sequence, The first signal is represented as A[n], and the second signal B 10 [n] is a constant when corresponding to the specific symbol, or the second signal B 11 [n] is a constant when corresponding to the symbol at the center of the specific symbol sequence, and the modulation local signal is a pulse signal.

[0285] (Appendix 12) The device according to Appendix 1, The analog characteristics are the static and dynamic analog characteristics of each stage in a transmitter having a structure in which a plurality of stages of modulators are cascaded, The first signal in the measurement waiting stage is A (s) [n], and the first signal in the non-measurement waiting stage is A (w) [n]=0, w≠s, The second signal is B (s) 12(q) =A (s) [n], and the B (s) 12(q) is sequentially input into the second electro-optical converter respectively to generate a modulation local signal

[0286]

Number

[0287]

Number

[0288] (Appendix 13) The device according to Appendix 1, Further comprising a quantization unit that quantizes the first signal or the second signal using at least one bit, and inputs the quantized signal to the second electrical-optical converter to obtain the modulated local signal.

[0289] (Appendix 14) 10. The apparatus of claim 1, the first electrical-optical converter is a transmitter itself, or a modulation unit of a part of a transmitter, or a directly modulated laser; The second electrical-to-optical converter outputs a limited number of states.

[0290] (Appendix 15) 10. The apparatus of claim 1, the first electro-optical converter and the second electro-optical converter are connected in parallel, the first electro-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, and the second electro-optical converter generates the modulated local signal based on the optical carrier and the second signal; The optical signal to be measured and the modulated local signal are respectively input to an opto-electrical multiplier to obtain a product electrical signal, and the product electrical signal is electrically averaged to generate the at least one correlation quantity.

[0291] (Appendix 16) 10. The apparatus of claim 1, the first electro-optical converter and the second electro-optical converter are connected in series, the first electro-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, and the second electro-optical converter generates the modulated local signal based on the optical signal to be measured and the second signal; The modulated local signal is input to an optical-electrical converter to obtain an electrical signal, and the electrical signal is electrically averaged to generate the at least one correlation quantity.

[0292] (Appendix 17) 1. A method for monitoring analog characteristics of an optical transmitter, comprising: inputting the first signal into a first electrical-optical converter to obtain an optical signal to be measured; inputting a second signal into a second electro-optical converter to obtain a modulated local signal, the second signal being determined based on the first signal and the monitored analog characteristics of the first electro-optical converter; performing a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and estimating an analog characteristic of the first electrical-to-optical converter based on the correlation amount.

[0293] (Appendix 18) An optical transmitter, a first electro-optical converter and a second electro-optical converter; a first signal is input to the first electro-optical converter to obtain an optical signal to be measured, a second signal is input to the second electro-optical converter to obtain a modulated local signal, and the second signal is determined based on the first signal and an analog characteristic to be monitored of the first electro-optical converter; the optical transmitter further includes a monitoring device; The monitoring device performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and estimates an analog characteristic of the first electrical-optical converter based on the correlation quantity.

Claims

1. 1. An apparatus for monitoring analog characteristics of an optical transmitter, comprising: a first input unit for inputting a first signal to a first electrical-optical converter to obtain an optical signal to be measured; a second input unit for inputting a second signal to a second electro-optical converter to obtain a modulated local signal, the second signal being determined based on the first signal and the monitored analog characteristics of the first electro-optical converter; a correlation unit that performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and an estimation unit for estimating an analog characteristic of the first electrical-to-optical converter based on the correlation quantity;

2. 10. The apparatus of claim 1, The apparatus, wherein the correlation quantity represents a value at a first time of an impulse response when the first electro-optical converter and the second electro-optical converter are cascaded, the first time being dependent on a relative delay between the first signal and the second signal.

3. 10. The apparatus of claim 1, An apparatus, when a transmitter transmits at least two superimposed signals, monitoring each signal at least once to obtain at least two correlation quantities, and estimating an analog characteristic of the first electrical-to-optical converter based on the at least two correlation quantities.

4. 10. The apparatus of claim 1, the analog characteristic being the frequency-independent IQ imbalance of a coherent transmitter; The first signal is A[n]=A Ｉ [n] + jA Ｑ [n], and A Ｉ [n] and A Ｑ [n] respectively represent the signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B Ｉ １ [n] = A Ｉ [n] and B Ｑ １ [n] = A Ｑ [n] and B Ｉ １ [n] and B Ｑ １ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 1] and [Equation 2] or The second signal is B Ｉ ２ [n] = A Ｉ [n] + A Ｉ [n-1]+...+A Ｉ [n−k] and B Ｑ ２ [n] = A Ｑ [n] + A Ｑ [n-1]+...+A Ｑ [n−k], k=1, 2, ..., K, and B Ｉ ２ [n] and B Ｑ ２ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 3] and [Equation 4] A device that generates

5. 10. The apparatus of claim 1, the analog characteristic is an IQ deviation of a coherent transmitter; The first signal is A[n]=A Ｉ [n] + jA Ｑ [n], and A Ｉ [n] and A Ｑ [n] respectively represent the signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B Ｉ ３ [n] = A Ｉ [n]-A Ｉ [n-m] and B Ｑ ３ [n] = A Ｑ [n]-A Ｑ [n-m], m=1, 2, ..., M, and B Ｉ ３ [n] and B Ｑ ３ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 5] A device that generates

6. 10. The apparatus of claim 1, the analog characteristic is a frequency-related IQ imbalance of a coherent transmitter; The first signal is A[n]=A Ｉ [n] + jA Ｑ [n], and A Ｉ [n] and A Ｑ [n] respectively represent the signals loaded onto the I and Q paths of the coherent transmitter; The second signal is B Ｉ／Ｑ ４（ｑ） [n] = A Ｉ／Ｑ [n] and B Ｉ ４（ｑ） [n] and B Ｑ ４（ｑ） [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 6] where 1≦q≦Y, q is an integer, Y is an empirical value selected based on the analog characteristics of the transmitter to be measured, and τ is a unit delay less than T, or (q-1)τ=mT+δ, and when 0≦δ<T, the second signal is B Ｉ／Ｑ ４（ｑ） [n] = A Ｉ／Ｑ [nm], and B Ｉ ４（ｑ） [n] and B Ｑ ４（ｑ） [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 7] A device that generates

7. 10. The apparatus of claim 1, The analog characteristic is a frequency-independent difference between different stages or different stage combinations allocated according to bits in the transmitter, The first signal is the signal A that is loaded into the stage or stage combination assigned by the j-th bit. （ｊ） [n], The second signal is B （ｊ） ５ [n] = A （ｊ） [n], and B （ｊ） ５ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 8] or The second signal is B （ｊ） ６ [n] = A （ｊ） [n] + A （ｊ） [n-1]+...+A （ｊ） [n−k], k=1, 2, . . . , K, and （ｊ） ６ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 9] A device that generates

8. 10. The apparatus of claim 1, the analog characteristic is a deviation difference between different stages or different stage combinations allocated according to bits in the transmitter; The first signal is the signal A that is loaded into the stage or stage combination assigned by the j-th bit. （ｊ） [n], The second signal is B （ｊ） ７ [n] = A （ｊ） [n]-A （ｊ） [nm], and B （ｊ） ７ [n] are sequentially input to the second electro-optical converter, respectively, to form a modulated local signal [Equation 10] A device that generates

9. 10. The apparatus of claim 1, the analog characteristic being a frequency-related difference between different stages or stage combinations allocated according to bits in the transmitter; The first signal is the signal A that is loaded into the stage or stage combination assigned by the j-th bit. （ｊ） [n], The second signal is B （ｊ） ８（ｑ） =A （ｊ） [n], and B （ｊ） ８（ｑ） are sequentially input to the second electrical-optical converter, thereby forming a modulated local signal [0011] where 1≦q≦Y, q is an integer, Y is an empirical value selected based on the analog characteristics of the transmitter to be measured, and τ is a unit delay less than T, or (q-1)τ=mT+δ, and when 0≦δ<T, the second signal is B （ｊ） ８（ｑ） =A （ｊ） [nm], and B （ｊ） ８（ｑ） are sequentially input to the second electrical-optical converter, thereby forming a modulated local signal [0012] A device that generates

10. 10. The apparatus of claim 1, The analog characteristic is a difference between different stages or different stage combinations assigned according to bits across or within different polarization states in a dual polarization transmitter; H and V represent the H and V polarization states of the dual-polarized transmitter, respectively; The second signals of the H path and V path of the dual polarization transmitter are B Ｈ ９ [n] and B Ｖ ９ [n] An apparatus.

11. 10. The apparatus of claim 1, the analog characteristic is an analog characteristic of the first electrical-to-optical converter under a specific symbol or a specific symbol sequence; The first signal is represented as A[n], and the second signal (B １０ [n]) is a constant when it corresponds to the particular symbol, or １１ [n]) is a constant when it corresponds to a center symbol of the particular symbol sequence, and the modulated local signal is a pulse signal.

12. 10. The apparatus of claim 1, The analog characteristics are static and dynamic analog characteristics of each stage in a transmitter having a structure in which multiple stages of modulators are cascaded, The first signal in the measurement waiting stage is A （ｓ） [n], and the first signal in the non-measurement waiting stage is A （ｗ） [n]=0, w≠s, The second signal is B （ｓ） １２（ｑ） =A （ｓ） [n], and B （ｓ） １２（ｑ） are sequentially input to the second electrical-optical converter, thereby forming a modulated local signal [0013] where 1≦q≦Y, q is an integer, and τ is a unit delay less than T, or (q-1)τ=mT+δ, and when 0≦δ<T, the second signal is B （ｓ） １２（ｑ） =A （ｓ） [nm], and B （ｓ） １２（ｑ） are sequentially input to the second electrical-optical converter, thereby forming a modulated local signal [0014] A device that generates

13. 10. The apparatus of claim 1, The apparatus further includes a quantization unit that quantizes the first signal or the second signal using at least one bit, and inputs the quantized signal to the second electrical-to-optical converter to obtain the modulated local signal.

14. 10. The apparatus of claim 1, the first electrical-optical converter is a transmitter itself, or a modulation unit of a part of a transmitter, or a directly modulated laser; The second electrical-to-optical converter outputs a limited number of states.

15. 10. The apparatus of claim 1, the first electro-optical converter and the second electro-optical converter are connected in parallel, the first electro-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, and the second electro-optical converter generates the modulated local signal based on the optical carrier and the second signal; The optical signal to be measured and the modulated local signal are respectively input to an opto-electrical multiplier to obtain a product electrical signal, and the product electrical signal is electrically averaged to generate the at least one correlation quantity.

16. 10. The apparatus of claim 1, the first electro-optical converter and the second electro-optical converter are connected in series, the first electro-optical converter generates the optical signal to be measured based on an optical carrier and the first signal, and the second electro-optical converter generates the modulated local signal based on the optical signal to be measured and the second signal; The modulated local signal is input to an optical-to-electrical converter to obtain an electrical signal, which is electrically averaged to generate the at least one correlation quantity.

17. 1. A method for monitoring analog characteristics of an optical transmitter, comprising: inputting the first signal into a first electrical-optical converter to obtain an optical signal to be measured; inputting a second signal into a second electrical-to-optical converter to obtain a modulated local signal, the second signal being determined based on the first signal and the monitored analog characteristics of the first electrical-to-optical converter; performing a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and estimating an analog characteristic of the first electrical-to-optical converter based on the correlation measure.

18. An optical transmitter, a first electro-optical converter and a second electro-optical converter; a first signal is input to the first electro-optical converter to obtain an optical signal to be measured, a second signal is input to the second electro-optical converter to obtain a modulated local signal, and the second signal is determined based on the first signal and an analog characteristic to be monitored of the first electro-optical converter; the optical transmitter further includes a monitoring device; The monitoring device performs a correlation process on the optical signal to be measured and the modulated local signal to obtain at least one correlation quantity; and estimates the analog characteristics of the first electrical-optical converter based on the correlation quantity.

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