JP2003207538A - High frequency characteristic measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency characteristic measuring system capable of measuring various high frequency characteristics, for example, of a communication semiconductor laser, efficiently and highly accurately in a short time without reconnecting a high frequency cable or the like. <P>SOLUTION: This system is equipped with a plurality of signal generators for generating respectively a high-frequency signal for controlling emission of a device (semiconductor laser). A high-frequency relay circuit interposed in a high-frequency signal transmission path for connecting each signal generator to the semiconductor laser is switched, to thereby select the high-frequency signal applied to the semiconductor laser, and an optical path is switched by using an optical channel switch, to thereby introduce selectively a laser beam (output of the device) emitted by the semiconductor laser into a plurality of kinds of optical measuring instruments (measuring control means). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency characteristic measuring system capable of efficiently measuring various high frequency characteristics of, for example, a semiconductor laser for optical communication in a short time and with high accuracy.

[0002]

[Related background art] Recently, high-speed optical information media
The development of large-capacity information communication technology is remarkable. This kind of optical information communication uses a semiconductor laser as its light source,
It is performed by modulating the laser light output from the semiconductor laser according to communication information (data). At this time, if the modulated laser light is defective or the modulated laser light is unstable, it may cause a communication error. Therefore, it is necessary to use only a semiconductor laser whose operation characteristics and reliability are surely guaranteed. Is. Therefore, it is important to measure the high frequency characteristics of the semiconductor laser in advance and select only those having no defect (defect).

[0003]

By the way, the high frequency characteristics for evaluating the performance of the semiconductor laser for optical communication cover various items and are measured by using various measuring instruments. For example, when the eye pattern is measured, the semiconductor laser is driven to emit light by using a pulse pattern generator (PPG), and the output light thereof is measured by using an optical oscilloscope. When measuring the modulation frequency characteristic, chirping, etc., an optical spectrum analyzer, component analyzer, signal analyzer or the like is used as appropriate.

However, in general, conventionally, a high-frequency cable (high-frequency signal transmission line) or an optical fiber cable (optical signal transmission line) is added to each measuring instrument selected in accordance with the measurement content (item). The characteristics of the semiconductor laser are measured by reconnecting. Therefore, there is a problem that the measurement takes a lot of time and is troublesome. In addition, there is a problem in that the driving conditions of the semiconductor laser may change and the measurement accuracy may be affected by a slight difference in the torque pressure that tightens the high-frequency cable when it is reconnected. Such a problem also occurs when measuring various high-frequency characteristics in an electronic device including various high-frequency semiconductor elements.

Further, various characteristic parameters in the above-mentioned optical device and electronic device are correlated with each other. However, it is difficult to measure all of these characteristic parameters with individual measuring instruments, and it is necessary to switch the measuring instruments each time. Therefore, it is very difficult to comprehensively evaluate various high-frequency characteristics of optical devices and electronic devices while grasping the correlation between various characteristic parameters.

The present invention has been made in consideration of such circumstances, and an object thereof is to obtain various high frequency characteristics of an optical device such as a semiconductor laser for communication and an electronic device without reconnection of a high frequency cable. An object of the present invention is to provide a high-frequency measurement system that can perform efficient and highly accurate measurement in a short time.

[0007]

In order to achieve the above object, a high frequency characteristic measuring system according to the present invention measures various high frequency characteristics of an electronic device such as an optical device or a high frequency semiconductor element including a semiconductor laser for communication. A plurality of signal generators that respectively generate a plurality of types of high-frequency signals for controlling the drive of the device, and particularly in a high-frequency signal transmission line connecting each of these signal generators and the device. By switching the inserted high-frequency relay circuit according to the type of high-frequency characteristics to be measured, a high-frequency signal to be applied to the device is selected (measurement control means), while taking in the output of the device to determine the high-frequency characteristics of the device. It is characterized in that it is measured (claim 1).

That is, the measurement system according to the present invention is configured so that a plurality of types of high-frequency signals generated by a plurality of signal generators are selectively applied to a device such as a semiconductor laser using a high-frequency relay circuit. , It is not necessary to reconnect a high frequency cable between a plurality of signal generators and a semiconductor laser (device), which enables various high frequency characteristics of the semiconductor laser to be measured in a short time while keeping the measurement accuracy constant. The feature is that the measurement can be performed efficiently.

The high-frequency characteristic measuring system according to the present invention comprises a signal generator for generating a high-frequency signal for controlling the driving of the device, and particularly, the high-frequency characteristics of different types of the device are respectively provided. For a plurality of types of measuring instruments to be measured, the signal transmission path is switched using a channel switch according to the type of high-frequency characteristics to be measured (measurement control means), thereby selecting the output of the device to the measuring instrument. It is characterized in that it is introduced selectively (claim 2).

That is, in the measurement system according to the present invention, the light (modulated laser light) output from the semiconductor laser (device) is selectively introduced into a plurality of types of optical measuring instruments using, for example, an optical channel switch. It is characterized in that various high-frequency characteristics can be measured by selectively using the plurality of kinds of optical measuring instruments without changing the optical path (for example, optical fiber).

Further, in the high frequency characteristic measuring system according to the present invention, a high frequency relay circuit inserted in a high frequency signal transmission line connecting a plurality of signal generators and devices is switched according to the type of high frequency characteristic to be measured. A high-frequency signal to be applied to the device is selected, and a signal transmission path for transmitting the output of the device to a plurality of types of measuring instruments is switched using a channel switch according to the type of high-frequency characteristics to be measured. (Claim 3)

That is, the measuring system according to the present invention switches between the high-frequency relay circuit and the channel switch according to the type of high-frequency characteristics to be measured, so that, for example, a high-frequency cable (high-frequency signal transmission line) and an optical fiber ( The present invention is characterized in that various high-frequency characteristics can be measured by selectively using a plurality of types of optical measuring instruments described above without connecting the respective optical paths).

Preferably, the measurement control means controls the high-frequency relay circuit and / or the optical channel switch in order to perform a control operation so as to continuously measure a plurality of types of high-frequency characteristics of the device. 4). It should be noted that an output selection high-frequency relay circuit for selectively applying a high-frequency signal transmitted through the high-frequency signal transmission path to a plurality of devices is further provided, and the output selection high-frequency relay circuit is sequentially switched to the plurality of devices. It is also desirable to configure so that the high frequency characteristics of can be sequentially measured (claim 5).

Incidentally, the optical device comprises a semiconductor laser, an optical modulator, or an integrated semiconductor laser in which an optical modulator is integrated at the same time, and a signal line connecting the device and the measuring instrument comprises an optical fiber forming an optical path. (Claim 6). In this case, it is preferable that the high-frequency characteristic measuring system includes a bias setting unit that sets a driving condition of the semiconductor laser. Further, the electronic device is composed of a high-frequency semiconductor element, and in this case, the signal line connecting the device and the measuring device is a high-frequency signal transmission line for transmitting a high-frequency electric signal (claim 7).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A high frequency characteristic measuring system according to an embodiment of the present invention will be described below with reference to the drawings, taking a high frequency characteristic measuring system for a semiconductor laser as an example. FIG. 1 shows a schematic configuration of a characteristic measuring system according to this embodiment. Reference numerals 1a, 1b, to 1n are communication semiconductor lasers whose high-frequency characteristics are to be measured. These semiconductor lasers 1 (1a, 1b, to 1n) may be direct modulation type semiconductor lasers capable of directly modulating the output light, or modulator integrated type semiconductor lasers in which optical modulators are simultaneously integrated. It may be.

This characteristic measuring system is provided with a plurality of signal generators 2 for respectively generating a plurality of types of high-frequency signals for controlling the light emission of the above-mentioned semiconductor laser 1 (1a, 1b, to 1n), in particular its modulation. The semiconductor laser 1 (1
a, 1b, to 1n) is provided with a plurality of types of optical measuring devices 3 for introducing (receiving) laser light (modulated light) output from the laser light (modulated light) and measuring the high-frequency characteristics thereof. By the way, the signal generators 2
Is composed of, for example, a signal analyzer 2a and a pulse pattern generator 2b. Further, the plurality of light measuring devices 3 are
For example, it comprises an optical oscilloscope 3a, an optical power meter 3b, an optical spectrum analyzer 3c, a BERT (bit error rate) measuring device 3d equipped with an O / E converter (not shown), and the like. The signal analyzer 2a
Also has a function as the light measuring device 3.

The high frequency characteristic measuring system includes a high frequency switch circuit 4 for selecting high frequency signals generated by the plurality of signal generators 2 (signal analyzer 2a, pulse pattern generator 2b). Then, the high frequency signal selected through the high frequency switch circuit 4 is
By giving the semiconductor laser 1 through the bias circuit 5, the driving (modulation) condition of the semiconductor laser 1 can be changed without switching the high-frequency cable (not shown) forming the high-frequency transmission path. It

The bias circuit 5 generates a bias current for defining the operating conditions of the semiconductor laser 1 and supplies it to the semiconductor laser 1 together with the high frequency signal. The bias adjusting circuit 6 sets the bias condition. To be done. Further, in this embodiment, the high frequency signal output from the bias circuit 5 is further passed through the output selecting high frequency relay circuit 7 to the semiconductor lasers 1a, 1b,
.About.1n are selectively applied.

On the other hand, this system was introduced from the light receiving section 8 when measuring the high frequency characteristics of the semiconductor laser 1 from the laser light (modulated light) output from the semiconductor laser 1 driven by receiving the high frequency signal. By selectively switching the optical path for guiding the laser light (modulated light) using the optical channel switch 9, the contents of the high frequency characteristics to be measured without switching the optical fiber cable (not shown) forming the optical path. The optical measuring device 3 (signal analyzer 2a, optical oscilloscope 3a, optical power meter 3b, optical spectrum analyzer 3c, BERT measuring device 3d, etc.) corresponding to the (type) is selected.

Incidentally, the high frequency relay circuit 4 and the optical channel switch 9 are switched and controlled by a computer forming a control unit 10 thereof according to the contents (type) of the high frequency characteristics of the semiconductor laser 1 to be measured (measurement items). Setting means 11). At this time, the control unit 10 (measurement item setting means 11) is interlocked with the switching of the high frequency relay circuit 4 and the optical channel switch 9 to selectively select the plurality of signal generators 2 and the plurality of types of optical measuring instruments 3. Control each operation. Further, when it is necessary to operate the signal generator 2 and the optical measuring instrument 3 in synchronization with each other, the control unit 10 may generate a synchronization signal to establish the synchronization between the two. The specific signal generator 2 (for example, the pulse pattern generator 2b) and the specific optical measuring device 3 (for example, the BERT measuring device 3d) may be connected in advance by using a high-frequency cable for transmitting the synchronization signal. good.

The operation of the bias adjusting circuit 6 is controlled by the controller 10 according to the driving conditions of the semiconductor laser 1 (measurement condition setting means 12). Further, the output switching high frequency relay circuit 7 includes a plurality of semiconductor lasers 1a,
Switching control is performed by the control unit 10 (measurement target switching unit 13) according to which of the semiconductor lasers 1 1b to 1n the high frequency characteristic is to be measured.

According to the communication semiconductor laser characteristic measuring system configured as described above, the control section (computer)
By controlling the switching of the high frequency relay circuits 4 and 7 and the optical channel switch 9 respectively under the control of 10, the contents (measurement items) of the high frequency characteristics to be measured can be obtained without reconnecting the high frequency cable or the optical fiber cable. By selectively using the corresponding signal generator 2 and the optical measuring device 3, the high frequency characteristics can be accurately measured. In particular, another measuring system (optical measuring device 3) is maintained while maintaining the operating conditions of the semiconductor laser 1 adjusted using a certain measuring system (optical measuring device 3).
By switching to, it becomes possible to continuously measure the high frequency characteristics over a plurality of types of items while aligning the characteristic parameters. Therefore, the reliability in comprehensively evaluating the high-frequency characteristics over a plurality of types of items can be dramatically improved.

Further, since it is not necessary to reconnect the high frequency cable or the optical fiber cable each time according to the type of high frequency characteristic to be measured, the workability is very good and the high frequency characteristic over a plurality of items is short. It can be measured efficiently in time. In addition, it is possible to suppress variations in measurement error caused by reconnection of the high frequency cable and the optical fiber cable and to perform highly accurate measurement.

By the way, according to the system configured as described above, the high frequency characteristics such as the eye pattern of the semiconductor laser 1, the modulation frequency characteristic, the optical spectrum, RIN (relative noise intensity), chirping and BERT are successively measured. It becomes possible to do. Moreover, a plurality of semiconductor lasers 1a,
By sequentially switching 1b to 1n, it becomes possible to continuously measure the above-mentioned high-frequency characteristics of each of the semiconductor lasers 1a, 1b to 1n.

Specifically, as illustrated in FIG. 2, I-L
Measurement [step S1], RIN measurement [step S2],
The eye pattern measurement [step S3], the spectrum measurement [step S4], and the BERT measurement [step S5] can be successively performed in sequence. Especially the first measurement (I
While setting the operating conditions of the semiconductor laser 1 based on the high frequency characteristics of the semiconductor laser 1 obtained by
The high frequency characteristics of other items thereafter can be efficiently measured.

That is, if the I-L characteristic of the semiconductor laser 1 is evaluated by the above-mentioned I-L measurement, it is possible to inspect a kink (a bend occurring on the I-L curve) in the semiconductor laser 1 according to the I-L characteristic. It will be possible. When the eye pattern is measured next, the extinction ratio at the specified power of the semiconductor laser 1 or the extinction ratio at the specified current is obtained by using the IL characteristic measured previously, or the current / relaxation oscillation frequency characteristic is obtained. , Optical output / relaxation oscillation frequency characteristics, current / RIN
It is possible to obtain the characteristics, the optical output / RIN characteristics, and the like.

With respect to the relaxation oscillation frequency, RIN measurement is performed while changing the bias current of the semiconductor laser 1, and the modulation signal (from the pulse pattern generator 2a when the relaxation oscillation frequency exceeds the modulation signal frequency). It is obtained by measuring a high frequency signal). By adopting such a measuring method, unnecessary measurement at a bias point where optical transmission is impossible can be omitted.

Further, by measuring the eye pattern of the modulated laser light, the modulation voltage / extinction ratio characteristic of the semiconductor laser 1, the modulation voltage / eye pattern measurement parameter, the modulation voltage at the specified extinction ratio, the specified current and the specified extinction ratio are obtained. The eye pattern measurement parameters, the eye pattern measurement parameters at the specified power and the specified extinction ratio, etc. can be obtained. For the extinction ratio, specify bias current or power, variably adjust the voltage of the pulse pattern generator 2b until the specified extinction ratio is obtained, and obtain data of the extinction ratio / pulse pattern generation voltage (modulation current). Measured by

Next, when the spectrum of the modulated laser light is measured, the spectrum characteristic at the specified extinction ratio and
It is possible to obtain the spectral characteristics at the designated power and the designated extinction ratio. At this time, by using the spectrum analyzer 2a, the chirping can be measured from the spectral characteristics at the designated power and the designated extinction ratio. At this time, if an optical fiber of a predetermined length is connected to the subsequent stage of the optical channel switch 9, it is possible to measure the chirping amount close to the actual usage pattern.

Further, B is connected via an optical fiber of an arbitrary distance length.
By performing the ERT measurement, for example, the bit error rate at the designated extinction ratio or the bit error rate at the designated power and the designated extinction ratio can be measured. That is, the high-frequency characteristics measured using a plurality of measurement systems,
The operating conditions (driving conditions) can be defined and associated with each other, and the measurement can be performed, and the correlation between high-frequency characteristics of different types can be accurately evaluated.

The above-described embodiment has been applied to the system for measuring the high frequency characteristics of the semiconductor laser. ) It can be similarly applied to the measurement of an optical device such as a modulator-integrated semiconductor laser. In this case, needless to say, when measuring only the high frequency characteristics of the optical modulator, the bios adjusting circuit for the semiconductor laser is not necessary. Then, while introducing the laser light guided from another light source into the optical modulator, a high frequency signal may be applied to the optical modulator to measure its high frequency characteristics.

In addition, without seeing such an optical device,
The same can be applied to the case of measuring the high frequency characteristics of an electronic device such as a high frequency semiconductor element. In this case, the electrical output signal of the electronic device may be guided to a predetermined measuring instrument via a high frequency signal transmission path such as a coaxial cable. Then, instead of the above-mentioned optical channel switch, the channel may be switched by using a high frequency relay circuit or the like. Even in the system configured as described above, it is possible to obtain the same effect as that of the above-described embodiment.

The present invention is not limited to the above embodiment. For example, the type and number of signal generators 2 connected to the semiconductor laser 1 via the high frequency relay circuit 4,
Further, the type and the number of the photodetectors 3 that detect the output light of the semiconductor laser 1 via the optical channel switch 9 may be determined according to the system specifications. Further, the measurement procedure of a plurality of types of high frequency characteristics, which is executed by controlling the switching of the high frequency relay circuit 4 and the optical channel switch 9, can be variously modified. The setting of the measurement procedure can be easily changed by changing the execution procedure of the measurement program in the control unit (computer) 10. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

[0034]

As described above, according to the present invention, various high frequency characteristics of a device such as a semiconductor laser can be shortened by selecting a plurality of types of measurement systems without switching high frequency cables or optical fiber cables. It can be measured efficiently in time. Moreover, various high-frequency characteristics can be associated with each other under predetermined operating conditions without causing variations in measurement errors due to reconnection of high-frequency cables and setting operating conditions according to the high-frequency characteristics of the semiconductor laser. It is possible to measure by the above, and its practical advantage is great.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of a high frequency characteristic measuring system for measuring characteristics of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a measurement procedure for various high-frequency measurements of a semiconductor laser.

[Explanation of symbols]

1, 1a, ~ 1c Semiconductor laser (device) 2,2a, 2b signal generator 3,3a, -3d optical measuring instrument 4 High frequency relay circuit 5 Bias circuit 6 Bias adjustment circuit High frequency relay circuit for 7 output selection 9 Optical channel switch 10 Control unit (computer)

Claims (8)

[Claims] 1. A system for measuring high frequency characteristics of an optical device or an electronic device, comprising: a plurality of signal generators respectively generating a plurality of types of high frequency signals for controlling driving of the device; and signal generators thereof. And a high-frequency signal transmission line that connects the device and a high-frequency relay circuit that selects the plurality of types of high-frequency signals and applies the high-frequency signals to the device, and captures the output of the device to measure the high-frequency characteristics of the device. A high frequency characteristic measuring system comprising: a measuring instrument; and a measurement control unit that switches and sets the high frequency relay circuit according to the type of high frequency characteristic of the device to be measured. 2. A system for measuring high-frequency characteristics of an optical device or an electronic device, which is a signal for generating a high-frequency signal for controlling driving of the device and applying the high-frequency signal to the device via a high-frequency signal transmission path. A generator, a plurality of types of measuring instruments that respectively capture the output of the device and measure different types of high-frequency characteristics of the device, and a signal line that connects the device and each of the measuring instruments to each other to switch the device. A high-frequency characteristic comprising: a channel switch for selectively introducing an output into each of the measuring instruments; and a measurement control unit for switching and setting the channel switch according to the type of the high-frequency characteristic to be measured by the device. Measuring system. 3. A system for measuring high frequency characteristics of an optical device or an electronic device, comprising: a plurality of signal generators respectively generating a plurality of types of high frequency signals for controlling driving of the device; A high-frequency relay circuit that is inserted in a high-frequency signal transmission path that connects each of the generators and that selects the plurality of types of high-frequency signals and applies the high-frequency signals to the device; and a high-frequency wave of a different type of the device that captures the output of the device A plurality of types of measuring instruments that respectively measure the characteristics, a channel switch that selectively introduces the output of the device to each of the measuring instruments by switching the signal lines that respectively connect the device and each of the measuring instruments, and the device Switching between the high frequency relay circuit and the channel switch is set according to the type of high frequency characteristics to be measured. Frequency characteristic measuring system characterized by comprising a measurement control means for. 4. The measurement control means switches the high frequency relay circuit and / or the channel switch in order to execute continuous measurement of a plurality of types of high frequency characteristics of the device. The high frequency characteristic measuring system according to any one of the above. 5. The high frequency characteristic measuring system according to claim 1, further comprising: a high frequency relay for output selection, which selectively applies a high frequency signal transmitted through the high frequency signal transmission path to a plurality of devices. A high frequency characteristic measuring system comprising a circuit. 6. The optical device comprises a semiconductor laser, an optical modulator, or an integrated semiconductor laser in which optical modulators are integrated simultaneously, and a signal line connecting the device and the measuring instrument is an optical fiber forming an optical path. The high frequency characteristic measuring system according to any one of claims 1 to 5. 7. The electronic device comprises a high frequency semiconductor element, and the signal line connecting the device and the measuring instrument comprises a high frequency signal transmission line for transmitting a high frequency electrical signal.
The high frequency characteristic measuring system according to any one of 1. 8. The high frequency characteristic measuring system according to claim 6, further comprising bias setting means for setting a driving condition of the semiconductor laser.