JP5485496B2 - Semiconductor test equipment - Google Patents

Description

  The present invention relates to a jitter adding apparatus and a semiconductor test apparatus. More specifically, the present invention relates to a jitter adding apparatus that adds desired jitter to signal light, and a test apparatus including the jitter adding apparatus.

There are various methods and apparatus for testing semiconductor optical devices that emit or receive signal light. In particular, there is a test apparatus for testing by adding jitter to signal light in order to test the tolerance to jitter in an optical device (for example, Patent Document 1). Patent Document 1 below describes that jitter is superimposed on an electrical test signal, the test signal on which jitter is superimposed is converted into an optical signal, and used as a test signal for an optical communication system.
JP 2006-041681 A

  However, when jitter is superimposed on an electrical test signal, the response speed of the electrical signal is limited, so it is difficult to superimpose a small amount of jitter on the test signal. In addition, the electric circuit cannot add jitter directly to the optical signal. For this reason, for example, even when trying to independently evaluate the jitter tolerance of the optical signal receiving side in the loopback test of the optical input / output module, asynchronous jitter may be added to the optical signal generated on the transmitting side. Can not.

  Accordingly, in order to solve the above-described problem, as a first embodiment of the present invention, an optical jitter adding apparatus for adding jitter to signal light that is pulsed light having a specific wavelength and outputting the signal light, the control light having different wavelengths. When a signal light is input, a signal light of a specific wavelength is output as non-converted light, and one of the control lights having different wavelengths and the signal light are temporally superimposed and input. The wavelength conversion element that outputs the converted light obtained by converting the wavelength of the signal light to the conversion wavelength different from the specific wavelength, corresponding to the wavelength of the control light, and the non-converted light and the converted light output from the wavelength conversion element. Is provided with a delay unit that adds a jitter to the signal light and outputs the delayed signal light.

  Furthermore, as a second embodiment of the present invention, there is provided a semiconductor test apparatus for testing a semiconductor optical device by adding jitter to signal light which is pulsed light of a specific wavelength, and an electrical device for generating signal light in the semiconductor optical device. A signal generator that generates a test signal, a control light source that outputs control light having different wavelengths, and when signal light is input, the signal light having a specific wavelength is output as non-converted light. If any of the control lights of different wavelengths are input in a time-superimposed manner, the converted light converted from the signal light wavelength to a conversion wavelength different from the specific wavelength corresponding to the control light wavelength is output. And a delay unit that receives the non-converted light and the converted light output from the wavelength converting element and delays them with a different delay amount according to the wavelength, thereby adding jitter to the signal light and outputting it. Equipped with a.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. Therefore, a sub-combination of these feature groups can also be an invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram schematically showing the configuration of an optical jitter adding apparatus 10 that adds jitter to an optical signal. As shown in the figure, the optical jitter adding apparatus 10 includes a wavelength variable control light source 30 different from the signal light source 20 that generates signal light, and an optical fiber 71, an output of the signal light source 20 and the wavelength variable control light source 30. And a delay unit 200 connected to the output of the wavelength conversion unit 100 via an optical fiber 73. Further, a wavelength control signal generating unit 32 that generates a wavelength control signal for selecting the wavelength of the control light output from the wavelength variable control light source 30 is provided.

The signal light source 20 generates pulsed light having a specific wavelength λ ₁ whose pulse width and pulse interval are modulated into a predetermined pattern for testing. In this case, the signal light source 20 generates the pulsed light based on an electrical test signal having a predetermined pattern generated by the pattern generator of the semiconductor test apparatus. On the other hand, the wavelength tunable control light source 30 receives a wavelength control signal generated by the wavelength control signal generation unit 32, and has a wavelength selected from a plurality of mutually different wavelengths λ ₁₁ , λ ₁₂ , and λ _13. Light 35 is generated. An example of the signal light source 20 is a pulse laser, but is not limited thereto, and may be a combination of a CW laser and a modulator. On the other hand, an example of the wavelength variable control light source 30 is a DFB laser, for example. The DFB laser can generate pulsed light by ON-OFF control in units of one pulse.

  The wavelength conversion unit 100 multiplexes both the signal light 25 output from the signal light source 20 and the control light 35 output from the wavelength variable control light source 30 and couples it to the wavelength conversion element 120. And a wavelength conversion element 120 that receives the output. Here, when the signal light 25 is input to the wavelength conversion unit 100 alone, the wavelength conversion element 120 outputs the signal light 25 with the same wavelength. On the other hand, when both the signal light 25 and the control light 35 are input, the wavelength of the signal light 25 is converted according to the wavelength of the control light 35 and the converted light 45 is output, as will be described later. For convenience of explanation, in the following description, all of the optical signals output from the wavelength conversion element 120, including the light output from the wavelength conversion element 120 without being converted from the wavelength of the signal light 25, are used. This is referred to as converted light 45.

  The delay unit 200 receives the converted light 45 output from the wavelength conversion unit 100. The input converted light 45 is injected into the optical delay line 210 via the optical circulator 220. The optical delay line 210 gives a different amount of delay according to the wavelength of the input converted light 45 and returns it to the optical circulator 220 again as delayed light. The optical circulator 220 couples the delayed light input from the optical delay line 210 to the optical fiber 75 and outputs it as the output light 55 to the outside.

  Here, the optical delay line 210 itself is an optical fiber, and further includes a plurality of fiber grating portions 212, 214, 216, and 218 formed at different positions in the length direction. Each of the fiber grating portions 212, 214, 216, and 218 has a plurality of gratings formed at regular intervals to form a Bragg grating. The Bragg grating is centered on a wavelength (hereinafter referred to as “Bragg wavelength”) obtained by doubling the product of the refractive index of the optical fiber formed with the grating and the difference in refractive index changed in the grating. Reflects narrowband light. Therefore, each of the fiber grating sections 212, 214, 216, and 218 reflects light having a specific wavelength. Since the distances from the incident end of the optical delay line 210 to each of the fiber grating portions 212, 214, 216, and 218 are different from each other, the path length of light from being incident on the optical delay line 210 to being emitted is converted light 45. It depends on the wavelength.

In the delay unit 200 of the optical jitter adding apparatus 10 shown in FIG. 1, the fiber grating unit 212 closest to the incident end of the optical delay line 210 has a Bragg wavelength λ ₁ equal to the wavelength λ ₁ of the signal light 25. To do. In addition, the Bragg wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ of the other fiber grating portions 214, 216, and 218 are sequentially increased.

In the jitter adding apparatus 10, the signal light source 20 outputs signal light 25 that is pulsed light having a specific wavelength λ ₁ . The wavelength variable control light source 30 outputs control light 35 having any wavelength selected by the wavelength control signal generated by the wavelength control signal generation unit 32 among the different wavelengths λ ₁₁ , λ ₁₂ , and λ _13. To do.

The wavelength conversion element 120 outputs the signal light 25 having the specific wavelength λ _{1 when} the signal light 25 is input alone. On the other hand, the wavelength converting element 120, wavelength lambda _11, lambda _12, when the control light 35 and signal light 25 having any of the lambda ₁₃ is input to overlap temporally, the wavelength of the control light 35 lambda ₁₁ , Λ ₁₂ , λ ₁₃ , the converted light 45 obtained by converting the wavelength λ ₁ of the signal light 25 into the converted wavelengths λ ₂₁ , λ ₂₂ , λ ₂₃ different from the specific wavelength λ ₁ is output. The delay unit 200 receives the signal light 25 and the converted light 45 output from the wavelength conversion element 120 and has different delay amounts Δt ₁ , Δt ₂ , Δt depending on the wavelengths λ ₁ , λ ₂₁ , λ ₂₂ , λ _{23. 3} is output with a delay.

  As described above, the optical jitter adding apparatus 10 can add desired jitter directly to an optical signal. Therefore, for example, in a loopback test of the optical input / output module, desired jitter can be added to the optical signal generated on the transmission side, and the jitter tolerance on the reception side can be independently evaluated.

FIG. 2 is a perspective view showing a structure of a PPLN (Periodically Poled LiNbO ₃ ) waveguide that can be used as the wavelength conversion element 120. As shown in the figure, the PPLN waveguide includes an LiNbO ₃ substrate 122 that is a nonlinear optical crystal whose polarization is inverted at a very short period, and an optical waveguide formed on the LiNbO ₃ substrate 122 so as to cross the polarization distribution that is inverted. 124. When two laser beams having different wavelengths are injected into the wavelength conversion element 120 having such a structure, the sum frequency light or difference frequency light of the laser beams is emitted.

The wavelength conversion element 120 can be formed by, for example, a periodically poled lithium niobate (PPLN) optical waveguide. The periodically poled lithium niobate optical waveguide is input with strong light intensity when the signal light 25 having the specific wavelength λ _{1 and} the control light 35 having any one of the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ are input. The converted light 45 having a wavelength of the difference frequency between the second harmonic of the other light and the other light is output. Therefore, the wavelength control signal generator 32 selects the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ of the control light 35 and converts the signal light 25 with high efficiency, thereby allowing the wavelength conversion element 120 to convert light having a desired wavelength. 45 can be output.

LiNbO ₃ is known to be damaged by visible light at room temperature. Therefore, it is preferable to add magnesium oxide or the like to increase the stability of the material. Further, in the wavelength conversion element as described above, the signal light 25 and the control light 35 which are TM mode linearly polarized light, or the TM mode included in the signal light 25 and the control light 35 are subject to conversion. Of the linearly polarized light component.

FIG. 3 is a diagram for explaining the operation of the wavelength conversion element 120 having the PPLN waveguide as described above. As shown in the figure, the wavelength conversion element 120 is injected with one of a plurality of control lights 35 having different wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ and a signal light 25 having a specific wavelength λ _1. . Here, when the light intensity of the signal light 25 is sufficiently high, the second harmonic of the signal light 25 is generated, and the wavelengths λ ₂₁ , λ ₂₂ , corresponding to the difference frequency between the control light 35 and the second harmonic, converted light 45 having a lambda ₂₃ is emitted. Therefore, by selecting the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ of the control light 35 via the wavelength control signal generation unit 32, the wavelength of the converted light 45 is set to one of the wavelengths λ ₂₁ , λ ₂₂ , and λ _23. Can do.

The structure of the wavelength conversion element 120 is not limited to the PPLN waveguide. For example, LiB ₃ O ₅ , BaB ₂ O ₄ , KTiOPO ₄ , LiTaO _3, etc. having a periodically poled structure. Can also be used. A similar effect can be obtained even if a nonlinear optical element such as a semiconductor optical amplifier SOA (Semiconductor Optical Amplifier) is used. A nonlinear optical fiber, an electroabsorption modulator, or the like can also be used.

  FIG. 4 shows the mutual relationship between the signal light 25 output from the signal light source 20 as pulsed light, the control light 35 output from the wavelength variable control light source 30 as pulsed light, and the converted light 45 output from the wavelength conversion unit 100. It is a figure which compares and shows a timing. Note that the converted light 45 includes light in which the control light 35 is not input and the wavelength of the signal light 25 is maintained as it is.

As shown in the figure, the signal light 25 is pulsed light having a wavelength λ ₁ having a predetermined rising and falling pattern. For the sake of explanation, FIG. 4 shows pulsed light having a wavelength λ ₁ that rises at a constant interval and has a constant pulse width. On the other hand, the control light 35 becomes pulse light including a one-shot pulse that rises at a timing synchronized with a specific pulse of the signal light 25. The control light 35 has a constant pulse width, but each of the pulses has individual wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ . Here, since the pulse width of the control light 35 is equal to the pulse width of the signal light 25, it is preferable to make it wider. However, the pulse width of the control light 35 is preferably limited to a width that does not affect other pulses adjacent to the specific pulse of the signal light 25 to be subjected to wavelength conversion.

The signal light 25 and the control light 35 incident on the wavelength conversion unit 100 are combined in the optical coupler 110 while being synchronized in units of pulses, and then injected into the wavelength conversion element 120. The converted light 45 emitted from the wavelength conversion element 120 corresponds to the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ of the control light 35 in a period in which the pulse of the signal light 25 and the pulse of the control light 35 are temporally superimposed. And pulses having wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ that have been wavelength-converted. On the other hand, when the signal light 25 is incident on the wavelength conversion element 120 alone, that is, in a period in which there is no pulse (superimposed in time) corresponding to the control light 35 in FIG. The non-converted light that maintains the wavelength λ ₁ of the signal light 25 is emitted from the wavelength conversion unit 100. Therefore, the converted light 45 includes a pulse having the wavelength λ ₁ of the signal light 25 and a pulse having the wavelength-converted wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ .

FIG. 5 is a diagram comparing the timings of the converted light 45 and the output light 55 with each other. As described above, the optical delay line 210 of the delay unit 200 includes the fiber grating unit 212 having the same Bragg wavelength λ ₁ as the wavelength λ ₁ of the signal light 25. Each has fiber grating portions 214, 216, and 218 having unique Bragg wavelength Bragg wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ , respectively. Therefore, each pulse of the converted light 45 incident on the optical delay line 210 is reflected by the individual fiber grating sections 212, 214, 216, 218 according to the wavelengths λ ₁ , λ ₂₁ , λ ₂₂ , λ ₂₃ respectively. Is done.

Further, the fiber grating portions 212, 214, 216, and 218 have different distances from the incident end of the optical delay line 210. Therefore, the path length of light from entering the optical delay line 210 to exiting varies depending on the wavelengths λ ₁ , λ ₂₁ , λ ₂₂ , and λ ₂₃ of each pulse. Therefore, as shown in FIG. 5, according to the wavelength of the converted light 45, individual delay amounts Δt ₁ , Δt ₂ , and Δt ₃ are given to the pulses of the output light 55. In other words, a desired magnitude of jitter can be added to the output light 55 by selecting the wavelength of the control light 35 generated by the variable wavelength control light source 30.

In this way, the delay unit 200 selectively reflects the input converted light 45 according to the specific wavelength λ ₁ and the converted wavelengths λ ₂₁ , λ ₂₂ , λ ₂₃ , respectively. 216 and 218 can be formed by using optical fibers formed in the passing direction of the signal light 25 and the control light 35. Thereby, with a simple structure, delays of different amounts Δt ₁ , Δt ₂ , Δt ₃ according to the wavelengths λ ₁ , λ ₂₁ , λ ₂₂ , λ ₂₃ can be generated.

In the above embodiment, jitter that is delayed with respect to the timing of the pulse of the signal light 25 is generated. However, by changing the arrangement of the fiber grating part 212 having the same Bragg wavelength λ ₁ as the wavelength λ ₁ of the signal light 25, the other fiber grating parts 214, 216, 218 are closer to the incident end of the optical delay line 210. By arranging, jitter advanced with respect to the pulse timing of the signal light 25 can be generated.

  The optical jitter adding apparatus 10 can add desired jitter by delaying the signal light 25 for each pulse. Further, in the signal processing related to the addition of jitter, the optical signal is not converted into an electric signal, so that the configuration of the apparatus can be simplified. In addition, signal degradation associated with photoelectric conversion does not occur. In addition, it is also possible to form the optical jitter adding unit 11 by combining the wavelength conversion unit 100 and the delay unit 200 that are surrounded by a dotted line in FIG.

As described above, when the signal light 25 that is pulsed light having the specific wavelength λ ₁ is input and the jitter is added to the signal light 25 and output, the optical jitter adding unit 11 receives the signal light 25. When non-converted light having a specific wavelength λ ₁ is output and any one of the control lights 35 having different wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ and the signal light 25 are temporally superimposed, the control is performed. The converted light 45 corresponding to the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ of the light 35 and converted from the wavelength λ ₁ of the signal light 25 to the converted wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ different from the specific wavelength λ ₁ is output. The wavelength conversion element 120 and the signal light 25 and the conversion light 45 output from the wavelength conversion element 120 are input, and the delay amounts Δt ₁ , Δt ₂ , which differ depending on the wavelengths λ ₁ , λ ₂₁ , λ ₂₂ , λ ₂₃ , delay to output is delayed by Δt ₃ Light Jitter addition unit 11 and a 200 are provided. The optical jitter adding unit 11 can be attached to an existing optical signal transmission system to add a function for adding jitter.

In the above embodiment, the optical delay line 210 has the fiber grating portions 212, 214, 216, and 218 that reflect at different wavelengths arranged at different positions in the axial direction, but the configuration of the optical delay line 210 is not limited thereto. Absent. As another optical delay line 210, a chirped FBG whose pitch continuously changes in the axial direction so as to be reflected in a wavelength region including the wavelengths λ ₁ and λ ₂₃ may be used. In this case, the delay amount can be changed continuously by changing the wavelength of the converted light according to the wavelength of the control light.

  FIG. 6 is a diagram schematically showing the structure of the optical jitter adding apparatus 10 according to another embodiment. As shown in the figure, the optical jitter adding apparatus 10 uses an AWG (arrayed waveguide grating) instead of the optical delay line 210 of the delay unit 200 in contrast to the optical jitter adding apparatus 10 shown in FIG. The difference is that a delay unit 201 formed by using the delay unit 201 is provided. As shown in FIG. 6, the delay unit 201 includes an AWG (arrayed waveguide grating) demultiplexer 250 and a delay line 270 connected to the AWG demultiplexer 250. Also provided is a wavelength control signal generator 32 that generates a wavelength control signal for selecting the wavelength of the control light output from the wavelength variable control light source 30.

  The AWG duplexer 250 has a pair of slab waveguides 252 and 258 and a plurality of arrayed waveguides 254, 255, 256 and 257 arranged between them. This AWG demultiplexer 250 divides the non-converted light and the converted light included in the converted signal light 45 input from the wavelength conversion unit 100 via the optical fiber 73 according to the respective wavelengths, and slab waveguides in the subsequent stage At 258, output from a different waveguide.

  The delay line 270 includes a plurality of arrayed waveguides 274, 275, 276, 277, and a multiplexer 278. The plurality of arrayed waveguides 274, 275, 276, and 277 have different lengths. The delay line 270 inputs the respective lights output from the different waveguides of the AWG duplexer 250 to the corresponding plurality of arrayed waveguides 274, 275, 276, and 277. Output to the fiber 75. At this time, since the path length of the arrayed waveguide 274 is longer than that of the arrayed waveguide 275, for example, when converted light of the converted signal light 45 passes through the arrayed waveguide 274 and non-converted light passes through the arrayed waveguide 275, The converted light is delayed in time with respect to the non-converted light. Here, when the converted light passes through the arrayed waveguide 275 and the non-converted light passes through the arrayed waveguide 274, the temporal delay relationship between the converted light and the non-converted light in the delay unit output light 55 is reversed.

As described above, the delay unit 201 of the optical variable delay device 11 can output one of the non-converted light and the converted light with a time delay with respect to the other. As a result, as in the case of the optical delay line 210 shown in FIG. 5, the unique wavelength corresponding to the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ of the control light 35 selected under the control of the wavelength control signal generator 32. Jitter can be added to the pulses having the wavelengths λ ₂₁ , λ ₂₂ , and λ ₂₃ by giving delays according to the lengths of the optical waveguides 332, 234, 236, and 238.

  FIG. 7 is a diagram illustrating a structure according to another embodiment of the delay unit 202 described above. In the optical variable delay device 10 of FIG. 7, the same components as those of the optical variable delay device 10 of FIG. The delay unit 202 in FIG. 7 includes the AWG duplexer 250 shown in FIG. 6, optical fibers 281, 282, 283, 284 connected to the AWG duplexer 250, and these optical fibers 281, 282, 283. 284, and a multiplexer 278 connected to the H.284. According to such a configuration, by adjusting the lengths of the optical fibers 281, 282, 283, and 284, the path length through which the non-converted light and the converted light separated by the spectroscopic unit 231 pass can be set as desired. Can do. Therefore, the optical variable delay device 10 can add a larger jitter to one of the non-converted light and the converted light included in the delay unit output light 55 with respect to the other.

  FIG. 8 is a schematic diagram showing the structure of a wavelength tunable control light source 300 according to another embodiment. As shown in the figure, the wavelength variable control light source 300 includes a plurality of light emitting elements 312, 214, and 316 as light sources, power supplies 362, 364, and 366 that supply current to the light emitting elements 312, 314, and 316, Modulators 372, 374, and 376 for modulating the current are included. Here, the light emitting elements 312, 314, and 316 can change the wavelengths of the emitted lights 32, 34, and 36 in accordance with the current modulated by the modulators 372, 374, and 376. In this case, it is preferable that the ranges in which the wavelengths of the emitted lights 32, 34, and 36 output from the light emitting elements 312, 314, and 316 change are set adjacent to each other. Accordingly, the control light 38 that varies in a desired wide range can be generated without being limited to the wavelength range in which the single light emitting elements 312, 314, and 316 can emit light.

  In addition, the wavelength tunable control light source 300 is connected to the light emitting elements 312, 214, and 316 as outputs, and the outputs of the optical switches 322, 324, and 326 that individually interrupt each output and the outputs of the optical switches 322, 324, and 326 are single. And an optical multiplexer 340 for outputting as the control light 38. Further, the control light 38 is passed through an optical fiber amplifier 350 that compensates for optical signal attenuation in the optical switches 322, 324, and 326 and the optical multiplexer 340, and the optical coupler 110 of the wavelength conversion unit 100 shown in FIG. Combined with

  Here, the light emitting elements 312, 214, and 316 can change the emission wavelength within a certain range different from each other. The optical switches 322, 324, and 326 are selectively turned on by the control terminals 332, 334, and 336 that are selectively coupled to one drive source 338, and any one of the light emitting elements 312, 314, and 316 is selected. The emitted lights 32, 34, and 36 are output as the control light 38.

  FIG. 9 is a diagram for explaining the operation of the wavelength variable control light source 300 shown in FIG. As shown in the figure, during an initial period in which the wavelength of the control light 38 is relatively short, the optical switch 322 is turned on, and the emitted light 32 of the light emitting element 312 is output as the control light 38. The light emitting element 312 can change the wavelength of the emitted light 32 within a certain range.

  In the subsequent period, since the wavelength required for the control light 38 exceeds the range in which the light emitting element 312 can emit light, the optical switch 324 is turned on. Thereby, the emitted light 34 of the light emitting element 314 that emits light in a longer wavelength range is emitted as the control light 38. In the next period, since the control light 38 having a longer wavelength is required, the optical switch 326 is turned on. Thereby, the emitted light 36 of the light emitting element 316 that emits light in a longer wavelength range is emitted as the control light 38. In the subsequent period, conversely, the optical switches 324 and 322 are sequentially turned on. In this way, as indicated by the alternate long and short dash line in the figure, the control light 38 whose wavelength changes in a sine wave shape as a whole is output. Although the change in wavelength is a sine wave here, it is needless to say that other waveforms such as a sawtooth wave and a rectangular wave can be selected. It is also possible to form a random jitter histogram without a specific pattern.

  In the waveform of the control light 38 shown in FIG. 9, all the optical switches 322, 324, and 326 are blocked at the starting point, and the control light 38 is not emitted. The control light 38 is generated as a pulse signal synchronized with the signal light 25 in the optical jitter adding apparatus 10 shown in FIG. 1 or FIG.

FIG. 10 is a diagram showing the pulse timing of the output light 55 to which jitter has been added by the control light 38 shown in FIG. As shown in the figure, in the optical jitter addition apparatus 10 shown in FIG. 1 or FIG. 6, when the control light 38 having the waveform shown in FIG. The wavelength of the converted light 45 emitted from the unit 100 changes periodically. That is, the pulse of the signal light 25 during the period when the control light 38 is not emitted has the wavelength λ ₁ of the signal light 25 itself. Further, the wavelength λ _n of the converted light 45 in the period until the converted light 45 having the wavelength λ ₁ is emitted next changes periodically according to the change in the wavelength of the control light 38.

As described above, the wavelength variable control light source 300 can modulate and output the wavelength λ _n of the control light 35 in a sine wave form with respect to time. When such converted light 45 is incident, the delay units 200 and 202 give different delays according to the wavelength of the converted light 45 as described above. Therefore, as shown in the lower part of FIG. 9, the output light 55 is added with a sinusoidal jitter that changes periodically. In order to simplify the explanation, the change in the wavelength of the control light 38 is made sinusoidal in FIG. 9, but all jitters having a periodic change that can be expressed by Fourier series are called sinusoidal jitter. This is one of the typical patterns of test signals in the semiconductor test apparatus 400.

  FIG. 11 is a diagram schematically showing the structure of the entire semiconductor test apparatus 400 that can be equipped with the optical jitter adding apparatus 10 as described above. As shown in the drawing, a semiconductor test apparatus 400 includes a handler 410 that physically operates a semiconductor device under test 424 and a test head including a performance board 422 loaded with the semiconductor device under test 424 sequentially supplied by the handler 410. 420 and a host device 430 that supplies data for a test signal to be applied to the semiconductor device 424 to be tested.

  Here, the host device 430 is connected to the test head 420 via the optical fiber cable 440 and supplies data. The test head 420 generates an electrical test signal based on the data, converts the electrical test signal generated by the signal generator into signal light, and adds the signal light jitter. An optical jitter adding device 10 is provided. As a result, desired jitter can be added to the signal light input to the semiconductor device under test 424.

  As described above, the optical jitter adding apparatus 10 can add a desired jitter to an input optical signal without electro-optical conversion or optical-electrical conversion. Therefore, it can be advantageously used for generating a test signal when evaluating the jitter tolerance of the optical digital circuit.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. Further, it is apparent from the description of the scope of claims that the embodiment added with such changes or improvements can be included in the technical scope of the present invention.

It is a schematic diagram which shows the structure of the optical jitter addition apparatus 10 which concerns on one embodiment. 3 is a perspective view showing a structure of a PPLN waveguide as a wavelength conversion element 120. FIG. 5 is a diagram for explaining the operation of a PPLN waveguide as a wavelength conversion element 120. FIG. It is a figure which shows the mutual pulse timing of the signal light 25, the control light 35, and the conversion light 45. FIG. It is a figure which shows the pulse timing of the conversion light 45 and the output light 55. FIG. It is a figure which shows typically the structure of the optical jitter addition apparatus 10 which concerns on other embodiment. It is a figure which shows the delay part 202 which concerns on other embodiment. It is a figure which shows the structure of the wavelength variable control light source 300 in other embodiment. It is a figure explaining the operation | movement of the wavelength variable control light source 300 shown in FIG. It is a figure which shows the pulse timing of the output light 55 to which the jitter was added by the control light 38 shown in FIG. It is a schematic diagram which shows the structure of the whole semiconductor test apparatus 400 which can mount the optical jitter addition apparatus 10 or the jitter addition unit 11. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical jitter addition apparatus, 11 Jitter addition unit, 20 Signal light source, 25 Signal light, 30, 300 Wavelength variable control light source, 32 Wavelength control signal generation part, 35, 38 Control light, 45 Conversion light, 55 Output light, 71, 72, 73, 74, 75, 252, 254, 256, 258 optical fiber, 100 wavelength converter, 110 optical coupler, 120 wavelength converter, 122 LiNbO ₃ substrate, 124, 232, 234, 236, 238, optical waveguide, 200, 202 delay unit, 210 optical delay line, 212, 214, 216, 218 fiber grating unit, 220 optical circulator, 230 substrate, 231 optical demultiplexer, 233, 340 optical multiplexer, 312, 314, 316 light emitting element, 322, 324, 326 Optical switch, 332, 334, 336 Control Child, 338 drive source, 350 an optical fiber amplifier, 400 a semiconductor test apparatus, 410 handler, 420 test head 422 performance board 424 a semiconductor device under test, 430 host device 440 an optical fiber cable,

Claims (7)

A semiconductor test apparatus for testing a semiconductor optical device by adding jitter to signal light which is pulse light of a specific wavelength,
A signal generator for generating an electrical test signal for generating a signal light in the semiconductor optical device;
A signal light source for generating signal light, wherein a pulse width and a pulse interval are modulated into a predetermined pattern based on a pattern of a test signal generated by the signal generator;
A wavelength control signal generator for generating a wavelength control signal for selecting one of different wavelengths based on jitter added to the test signal;
A control light source that outputs control light having a wavelength corresponding to the wavelength control signal;
When the signal light is input, the signal light of the specific wavelength is output as non-converted light, and either the signal light or control light of different wavelengths is temporally superimposed and input Is a wavelength conversion element that outputs a converted light obtained by converting the wavelength of the signal light to a conversion wavelength different from the specific wavelength corresponding to the wavelength of the control light;
A delay unit that receives the non-converted light and the converted light output from the wavelength conversion element and delays the signal light by a different delay amount according to the wavelength; Prepared,
The control light source includes a plurality of light sources that are adjacent to each other in a range in which a wavelength of an optical signal to be output changes, and an optical switch that selectively outputs an optical signal output from any of the plurality of light sources to the outside Test equipment.   The control light source further includes a plurality of modulators that modulate a current of a power source supplied to each of the plurality of light sources, and an optical multiplexer that outputs an output of the optical switch as a single control light. The semiconductor test apparatus described.   The semiconductor test apparatus according to claim 1, wherein the control light source modulates the wavelength of the control light in a sine wave shape with respect to time and outputs the modulated signal.   The wavelength conversion element has a periodic periodic polarization inversion structure that outputs the converted light having a wavelength of a difference frequency between the second harmonic of one of the input signal light and the control light and the other. The semiconductor test apparatus according to claim 1.   The delay unit is connected to each of the spectroscopic unit that splits the input non-converted light and the converted light into a plurality of paths according to the wavelength, and a plurality of light beams having different path lengths. 5. The semiconductor test apparatus according to claim 1, further comprising: a waveguide, and an output unit that outputs the non-converted light and the converted light propagated through the plurality of optical waveguides on the same path. 6.   The delay unit includes a plurality of fiber gratings (FBGs) that selectively reflect the input non-converted light and converted light in accordance with the wavelengths thereof in the passing direction of the non-converted light and the converted light. The semiconductor test apparatus according to claim 1, comprising a formed optical fiber. The delay unit is a chirped that selectively reflects the input non-converted light and the converted light at a position corresponding to a wavelength, with a pitch continuously changing in a passing direction of the non-converted light and the converted light. The semiconductor test apparatus according to claim 1, comprising an optical fiber on which an FBG is formed.

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