JP2002296432A - Light wavelength bandpass filter and optical module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and low cross talk optical module for wavelength multiplexing and demultiplexing. SOLUTION: Array waveguide type gratings 9 (9a to 9d) for bandpass are respectively connected to five optical output waveguides 26 of an array waveguide type grating 20 for multiplexing and demultiplexing which functions as an optical wavelength multiplexing and demultiplexing device. Each array waveguide type grating 9 for the band passes pairs one light input port and one optical output port. The grating 9 transmits light with wavelengths centered on different light transmission central wavelengths with each other by respective input/output port pairs. Therefore, light with a plurality of wavelengths is transmitted and the optical background cross talk of each wavelength is reduced in a lump. For example, light with light transmission central wavelengths λ1, λ2, λ3, λ4, and λ5 outputted from the array waveguide type grating 20 for multiplexing and demultiplexing is made incident on light input ports 2a, 2b, 2c, 2d, and 2e of array waveguide type grating 9a for bandpass, and is outputted from optical output ports 6b, 6e, 6c, 6a, and 6d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength bandpass filter used for optical communication such as wavelength multiplexing optical communication and an optical module using the same.

[0002]

2. Description of the Related Art In recent years, in optical communication, as a method for dramatically increasing the transmission capacity, research and development on optical wavelength division multiplexing have been actively carried out, and practical use has been progressing. Optical wavelength division multiplexing, for example, is for multiplexing and transmitting a plurality of lights having different wavelengths from each other. By increasing the number of multiplexes, it is possible to efficiently increase the transmission capacity of one optical fiber. . Recently, a wavelength division multiplexing communication system using more than 100 wavelengths has been commercialized.

One of the optical components that plays an important role in this wavelength division multiplexing communication is an optical wavelength multiplexer / demultiplexer. An optical wavelength multiplexer / demultiplexer is a general term for an optical wavelength multiplexer and an optical wavelength demultiplexer, and many optical wavelength multiplexers and optical wavelength demultiplexers have another function.

[0004] One of the optical wavelength multiplexer / demultiplexers that has been put into practical use is an arrayed waveguide type diffraction grating (AWG; Arr;
ayed Waveguide Grating). As shown in FIG. 16, for example, the arrayed waveguide type diffraction grating is formed by forming a silica glass-based waveguide forming region 10 on a substrate 1 formed of silicon or the like. A waveguide configuration as shown in the figure is formed.

The waveguide configuration of the arrayed waveguide type diffraction grating is as follows.
A first slab waveguide 23 is connected to the output side of one or more optical input waveguides 22 arranged side by side, and an array waveguide 24 is connected to the output side of the first slab waveguide 23. A second slab waveguide 25 is connected to the output side of the waveguide 24, and a plurality of light output waveguides 26 arranged in parallel are formed on the output side of the second slab waveguide 25. .

The arrayed waveguide 24 propagates light derived from the first slab waveguide 23, and is formed by arranging a plurality of channel waveguides 24a in parallel.
The lengths of adjacent channel waveguides 24a are different from each other by a set amount (ΔL). The optical output waveguides 26 are provided in correspondence with the number of signal lights having different wavelengths to be split or multiplexed by, for example, an arrayed waveguide type diffraction grating. Usually, a large number of waveguides 24a are provided, for example, 100. In the figure, for simplification of the drawing, these channel waveguides 24a, optical output waveguides 26 and optical input waveguides 22 are used. Each number is shown in a simplified manner.

[0007] An optical fiber (not shown) on the transmission side is connected to the optical input waveguide 22 so that wavelength multiplexed light is introduced. The light introduced into the slab waveguide 23 spreads due to its diffraction effect, enters the array waveguide 24, and propagates through the array waveguide 24.

The light propagating through the array waveguide 24 reaches the second slab waveguide 25, and is further transmitted to the optical output waveguide 2
The light is condensed and output to 6, and since the lengths of all the channel waveguides 24a of the arrayed waveguide 24 are different from each other, the phase of each light is shifted after propagating through the arrayed waveguide 24. The wavefront of the focused light is tilted according to the amount of deviation,
The light condensing position is determined by the inclination angle.

In the array waveguide type diffraction grating,
Assuming that the angle (diffraction angle) at which light is collected when light enters the second slab waveguide from the array waveguide is φ, this angle φ and the wavelength of the collected light (center wavelength of light transmission) λ Has a relationship as shown in the following equation (1).

[0010] _{n s · d · sinφ + n} c · ΔL = m · λ ····· (1)

[0011] n _s is the equivalent refractive index of the first, second slab waveguide, d is between channel waveguides, first, end interval of the second slab waveguide side, phi angle of diffraction, n _c Represents the equivalent refractive index of the array waveguide, ΔL represents the difference between the lengths of adjacent array waveguides, and m represents the diffraction order.

Here, assuming that the wavelength when the diffraction angle φ = 0 is λ ₀ , this wavelength λ ₀ is expressed by the following equation (2). The wavelength λ ₀ is generally called the center wavelength of the arrayed waveguide grating.

Λ ₀ = n _c ΔL / m (2)

Further, as shown in FIG. 23, the diffraction angle φ = 0
Assuming that the condensing position of the arrayed waveguide type diffraction grating is point O, the condensing position of the light having the diffraction angle φ _p is a point P different from the point O (a position shifted from the point O in the X direction). Collect light. Here, assuming that a distance in the X direction between O and P is x, (Equation 1) is established between the distance x and the wavelength λ.

[0015]

(Equation 1)

In _equation (1), L _f is the focal length of the second slab waveguide, and _ng is the group refractive index of the arrayed waveguide. Incidentally, the group index n _g of the arrayed waveguide, the effective refractive index n _c of the arrayed waveguide is given by equation (2).

[0017]

(Equation 2)

The above (Equation 1) is obtained by arranging and forming the input end of the optical output waveguide at a distance dx in the X direction from the focal point O of the second slab waveguide, whereby the light having a different wavelength by dλ is obtained. Means that it is possible to retrieve

Therefore, the light condensing positions of the lights having different wavelengths are different from each other, and the light output waveguides are formed at the positions so that the light having different wavelengths (demultiplexed light) can be converted into the light having different wavelengths. It can be output from the output waveguide.

That is, the arrayed waveguide type diffraction grating separates light of one or more wavelengths from multiplexed light having a plurality of different wavelengths input from the optical input waveguide and separates the light from each optical output waveguide. has an output for optical demultiplexing function, the light transmission center wavelength of the light demultiplexed it is proportional to the effective refractive index n _c of the length of the difference ([Delta] L) and the arrayed waveguide of the arrayed waveguide 24.

Since the arrayed waveguide type diffraction grating has the above characteristics, the arrayed waveguide type diffraction grating can be used as a wavelength division multiplexer for wavelength division multiplexing transmission.
For example, as shown in FIG. 16, when wavelength-division multiplexed light having wavelengths λ1, λ2, λ3,... Λn (n is an integer of 2 or more) is input from one optical input waveguide 22, The light is spread by the first slab waveguide 23, reaches the array waveguide 24, passes through the second slab waveguide 5, and is condensed at different positions depending on the wavelength as described above, and has different light outputs. The light enters the waveguides 26, passes through the respective optical output waveguides 26, and is output from the output end of the optical output waveguide 26.

By connecting an optical fiber for light output (not shown) to the output end of each light output waveguide 26, the light of each wavelength is extracted through the optical fiber. When an optical fiber is connected to each of the optical output waveguides 26 and the optical input waveguide 22 described above, for example, an optical fiber array in which connection end faces of the optical fibers are fixed in a one-dimensional array is prepared. Is fixed to the connection end face side of the optical output waveguide 26 and the optical input waveguide 22 to connect the optical fiber to the optical output waveguide 26 and the optical input waveguide 22.

In the above-mentioned arrayed waveguide type diffraction grating, the light transmission characteristics (wavelength characteristics of the transmitted light intensity of the arrayed waveguide type diffraction grating) of the light output from each light output waveguide 26 are, for example, shown in FIG. ), And centering on each light transmission center wavelength (for example, λ1, λ2, λ3,... Λn),
The light transmission characteristics show that the light transmittance decreases as the wavelength shifts from the corresponding light transmission center wavelength. FIG. 18 schematically shows light transmission characteristics of light output from each light output waveguide 26 superimposed on one graph.

The light transmission characteristics do not always have one maximum value as shown in FIG. 17A, for example, and two or more light transmission characteristics as shown in FIG. 17B. In some cases.

Since the array waveguide type diffraction grating utilizes the principle of reciprocity (reversibility) of light, it has not only a function as an optical demultiplexer but also a function as an optical multiplexer. . That is, for example, as shown in FIG. 19, when lights of a plurality of wavelengths different from each other are made incident from the respective light output waveguides 26 for each wavelength, these lights pass through the propagation path opposite to the above and form an array. The light is multiplexed by the waveguide 24 and emitted from one optical input waveguide 22.

In such an arrayed waveguide type diffraction grating, as described above, since the wavelength resolution of the diffraction grating is proportional to the difference (ΔL) between the lengths of the channel waveguides of the arrayed waveguide, ΔL is designed to be large. By doing so, optical multiplexing and demultiplexing of wavelength-division multiplexed light with a narrow wavelength interval, which could not be realized by the conventional diffraction grating, becomes possible. A demultiplexing function, that is, a function of demultiplexing or combining a plurality of optical signals having a wavelength interval of 1 nm or less can be performed.

Further, the arrayed waveguide type diffraction grating is manufactured by forming the above-mentioned waveguide forming region from a glass material on a silicon substrate, and its manufacture is easy.
It is suitable for mass production.

By the way, light of a wavelength other than the signal light to be multiplexed / demultiplexed is not mixed into the optical wavelength multiplexer / demultiplexer such as the arrayed waveguide type diffraction grating as much as possible. It is required to be small.
In particular, background noise of wavelength characteristics is called background crosstalk, which is an important parameter because it affects all channels. FIG. 20 is a diagram showing the concept of background crosstalk (B in FIG. 20).

As shown in the figure, the background crosstalk is generally defined as the difference between the peak value of the spectrum and the average value of the overall transmitted light intensity at the base level.
It is often indicated by a negative value (in dB). The background crosstalk is centered on the signal light wavelength.
It may be represented by the difference between the transmitted light intensity in a certain band and the maximum value of the transmitted light intensity in the wavelength range including the band of the other channel, and is also indicated by a negative value (in dB).

In the arrayed waveguide type diffraction grating having the above structure, it is impossible in principle to eliminate the existence of crosstalk. Further, in the arrayed waveguide type diffraction grating, crosstalk increases due to an error in manufacturing the optical waveguide. This is because, in general, the array waveguide type diffraction grating having more channels and narrower channel spacing has a larger number of channel waveguides in the array waveguide, and the crosstalk is significantly deteriorated.

Recently, the technology of fabricating optical waveguides has been improved, and it has become possible to fabricate an arrayed waveguide type diffraction grating having a background crosstalk value of -30 dB or less. In the case of a waveguide grating, the sum of the crosstalk from another channel that enters one channel (total crosstalk) increases, which may cause a communication problem.

In order to reduce the total crosstalk, for example, an optical module as shown in FIG. 21 is used. In this optical module, optical fibers are provided in all the optical output waveguides 26 of an arrayed waveguide type diffraction grating (hereinafter, referred to as a multiplexing / demultiplexing / arrayed waveguide type diffraction grating) 20 functioning as an optical wavelength multiplexer / demultiplexer. 3, a band-pass filter 50 using a dielectric multilayer film is connected. In the drawing, reference numeral 40 denotes an input optical fiber for introducing wavelength-division multiplexed light into the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20.

Each of the band-pass filters 50 is a filter that transmits only a set wavelength band defined around a light transmission center wavelength of light output from the corresponding optical output waveguide 26. By cutting background crosstalk noise, total crosstalk can be reduced.

However, in the optical module shown in FIG. 21, a band-pass filter 50 is connected to each optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20, and each optical output waveguide is connected. Wave path 26 and each bandpass filter 50 are connected one-to-one through optical fiber 3.
Therefore, there is a problem that the optical module becomes large as a whole and the price becomes expensive.

Therefore, a plurality of (20 in the figure) arrayed waveguide type diffraction gratings (hereafter, referred to as "20") functioning as band-pass filters are provided on the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 as shown in FIG. An optical waveguide circuit is formed by arranging 9 band-pass / array waveguide type diffraction gratings 9 in parallel, and this optical waveguide circuit is connected to each optical input waveguide of the multiplexing / demultiplexing / array waveguide type diffraction grating 20. It has been proposed to connect each bandpass / array waveguide type diffraction grating 9 to 226 one-to-one. This proposal is described in abstract p134 of the 2000 IEICE Electronics Society Conference.

The bandpass / arrayed waveguide type diffraction grating 9 proposed above has one optical input waveguide 12 and one optical output waveguide 16, and the other waveguide configurations are combined. This is the same as the wave / array waveguide type diffraction grating 20. That is, as shown in the figure, the band-pass / array waveguide type diffraction grating 9 includes first and second slab waveguides 13 and 15.
And an arrayed waveguide 14 in which a plurality of channel waveguides 14a are arranged in parallel. The number of the channel waveguides 14a is different from the number of the channel waveguides 24a, and is appropriately set.

The light transmission center wavelength of the light transmitted through each bandpass / array waveguide type diffraction grating 9 is output from the corresponding optical output waveguide 26 of the multiplexing / demultiplexing / array waveguide type diffraction grating 20. The transmission band of the light of the band-pass / array waveguide type diffraction grating 9 is formed so as to coincide with the light transmission center wavelength of the light. It is more widely formed.

For example, the transmitted light intensity (spectrum) of light output from one optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is shown by a characteristic line a in FIG. The transmitted light intensity of the band-pass / array waveguide type diffraction grating connected to the optical output waveguide 26 is as shown by a characteristic line b in FIG. The spectrum shown by the characteristic line b is a spectrum that passes light in a wavelength band of a set band defined around the light transmission center wavelength (peak wavelength) of the characteristic line a.

The output from one of the optical output waveguides 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is connected to the bandpass / arrayed waveguide type diffraction grating connected to the optical output waveguide 26. The spectrum of the light output from the light output waveguide 16 of the grating 9 is as shown by the characteristic line c in FIG.

Accordingly, the output from each optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is output to the corresponding bandpass / arrayed waveguide type diffraction grating 9.
The light that enters the optical input waveguide 12 and is output from the optical output waveguide 16 of the band-pass / array waveguide type diffraction grating 9 has a background crosstalk centered on the respective light transmission center wavelengths. Spectrum becomes smaller.

In other words, the optical module formed by connecting the optical waveguide circuit shown in FIG. 22 to the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is the same as that of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20. As in the optical module of FIG. 21 in which a conventional conductive multilayer film band-pass filter 50 is connected to each optical output waveguide 26, it is possible to reduce background crosstalk noise and reduce total crosstalk. it can.

An optical module formed by connecting the optical waveguide circuit shown in FIG. 22 to the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 has a plurality of bandpass / arrayed waveguide type diffraction gratings 9. Is formed on a substrate and connected to the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20, the optical module becomes smaller than the optical module shown in FIG.

[0043]

However, the above proposal proposes a bandpass / array waveguide type diffraction grating 9 for each of the optical output waveguides 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20. For example, the optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is connected.
Array waveguide type diffraction grating 9 for the number of bandpasses
Must be provided. Therefore, when the wavelength demultiplexing number by the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 increases,
The number of band-pass / array waveguide type diffraction gratings 9 must be very large, and it is difficult to form them on one substrate.

The optical module proposed above is composed of the optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20.
The light transmission center wavelengths of a large number of band-pass / array waveguide type diffraction gratings 9 provided for the number of band-pass / array waveguide type diffraction gratings 20 are respectively set to the corresponding optical output waveguides 26 of the multiplexing / demultiplexing / array waveguide type diffraction grating 20.
However, there is a problem that the manufacture is very difficult because it must be manufactured accurately in accordance with the light transmission center wavelength of the light output from the device.

That is, as described above, the light transmission center wavelength of each band-pass / array waveguide type diffraction grating 9 is set to the corresponding optical output waveguide 26 of the multiplexing / demultiplexing / array waveguide type diffraction grating 20. Very high precision processing is required to match the light transmission center wavelength of the light output from the device, so that manufacturing is very difficult. Therefore, for example, FIG.
2, the light transmission center wavelength of all the bandpass / array waveguide type diffraction gratings 9 is 20 if the number of wavelengths demultiplexed by the multiplexing / demultiplexing / array waveguide type diffraction grating 20 becomes 40. To be accurate (to be the set wavelength)
It is almost impossible to form.

Therefore, in order to set the center wavelength of light transmission of each band-pass / arrayed waveguide type diffraction grating 9 to a set wavelength, the band-pass / arrayed-waveguide type diffraction grating 9 is manufactured and then its waveguide configuration is set. It is also conceivable to adjust the refractive index by irradiating high-intensity ultraviolet light, but it is necessary to irradiate (normally different) ultraviolet light individually to each band-pass / array waveguide type diffraction grating 9. This has to be very troublesome.

The optical module formed by connecting the above-mentioned band-pass / array waveguide type diffraction grating 9 is one of all band-pass / array waveguide type diffraction gratings 9.
If at least one of the characteristics is defective, the characteristics of the optical module become defective, so that the defect rate is increased and the yield is reduced.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical module which can perform signal light degradation due to crosstalk of an optical module even if the number of wavelengths to be multiplexed / demultiplexed is large. It is an object of the present invention to provide a small-sized and easily manufacturable optical wavelength bandpass filter capable of performing light multiplexing / demultiplexing while suppressing the optical wavelength and an optical module using the same.

[0049]

In order to achieve the above-mentioned object, the present invention has the following structure to solve the problem. That is, the optical wavelength bandpass filter of the first invention includes a diffraction grating, a plurality of light input ports for inputting light to the diffraction grating, and a plurality of light output ports for outputting light passing through the diffraction grating. A first light transmission center wavelength, which is input from one optical input port, is output from a corresponding optical output port, and the first light transmission input from another optical input port is provided. Each input / output port pair includes one optical input port and one optical output port, such that light centered on a second optical transmission center wavelength different from the central wavelength is output from the corresponding optical output port. Thus, the light transmission center wavelength different from each other is transmitted as a center, and this configuration is a means for solving the problem.

The optical wavelength bandpass filter according to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, further comprises the optical transmission center wavelengths of the light transmitted by the plurality of input / output port pairs, respectively, at substantially equal intervals. With this configuration, it is a means to solve the problem.

Further, in the optical wavelength bandpass filter according to the third aspect of the present invention, in addition to the configuration of the second aspect of the present invention, an interval between light transmission center wavelengths of light transmitted through the plurality of input / output port pairs is Δλ. When the number of the input / output port pairs is j, the central wavelength of light transmitted by one set input / output port pair of the diffraction grating when the diffraction order of the diffraction grating is M is λ _(M) , When the diffraction order of M is M-1, the light transmission center wavelength of light transmitted by the set input / output port pair of the diffraction grating is λ _(M-1), and when a predetermined set integer is i, λ _{( M-1)} = λ _(M) +
This is a means for solving the problem with a configuration that becomes Δλ (i + j). Here, Δλ is the channel spacing.

Further, an optical wavelength band-pass filter according to a fourth aspect of the present invention is a means for solving the problem with a configuration in which the set integer i is 0 in addition to the configuration of the third aspect.

Further, in the optical wavelength bandpass filter according to the fifth aspect, in addition to the configuration of the third or fourth aspect, the sum (i + j) of the set integer i and the number j of the input / output port pairs is provided.
Is a means for solving the problem with an odd number.

Further, in the optical wavelength bandpass filter according to the sixth aspect of the present invention, in addition to the configuration of any one of the first to fifth aspects, the diffraction grating may include one or more optical input waveguides arranged in parallel. A waveguide, and a first optical waveguide connected to an output side of the optical input waveguide.
A slab waveguide, an array waveguide connected to the output side of the first slab waveguide, a second slab waveguide connected to the output side of the array slab waveguide, and the second slab waveguide. A plurality of juxtaposed optical output waveguides connected to the output side of the waveguide, wherein the arrayed waveguides have respective lengths for propagating light derived from the first slab waveguide. This is a means for solving the problem with the configuration of an arrayed waveguide type diffraction grating in which a plurality of channel waveguides having different amounts are arranged in parallel.

Further, an optical wavelength band-pass filter according to a seventh aspect of the present invention has the configuration according to any one of the first to sixth aspects, and further includes a plurality of the diffraction gratings. The configuration formed on the same substrate is used as means for solving the problem.

Further, an optical module according to an eighth aspect of the present invention provides the optical wavelength bandpass filter according to any one of the first to seventh aspects, and a plurality of input / output port pairs of the optical wavelength bandpass filter. And a light wavelength multiplexer / demultiplexer for multiplexing / demultiplexing light having a wavelength corresponding to the wavelength of the light to be emitted.

Further, an optical module according to a ninth aspect of the present invention has a problem in that, in addition to the configuration of the eighth aspect, the optical wavelength bandpass filter and the optical wavelength multiplexer / demultiplexer are formed on the same substrate. It is a means to solve.

The optical wavelength bandpass filter of the present invention having the above-described configuration has a plurality of input ports for light to the diffraction grating and a plurality of output ports for light from the diffraction grating, each having one optical input port and one optical output port. This is a configuration in which each input / output port pair transmits light of a wavelength centered on a different light transmission center wavelength by each input / output port pair. There is an advantage in that the light transmission center wavelength can be easily formed as designed by applying a diffraction grating. .

When the optical wavelength bandpass filter of the present invention is connected to an optical wavelength multiplexer / demultiplexer such as an optical multiplexer / demultiplexer / array waveguide type diffraction grating, a plurality of optical outputs of the optical wavelength multiplexer / demultiplexer are connected. Since one optical wavelength band-pass filter of the present invention is connected to each of the optical wavelength division multiplexer / demultiplexers, the number of connections is smaller than that in the case where one optical wavelength band-pass filter is connected to one optical output unit of the optical wavelength multiplexer / demultiplexer. The number of optical wavelength band-pass filters to be used can be reduced.

The light output from each optical output unit of the optical wavelength multiplexer / demultiplexer enters the corresponding optical input port of the optical wavelength bandpass filter of the present invention, and the corresponding light of the optical wavelength bandpass filter. Output from the output port.

Therefore, the optical transmission center wavelength of the light transmitted and received by the plurality of input / output port pairs of the optical wavelength band-pass filter of the present invention is changed by the optical transmission center wavelength of the light multiplexed / demultiplexed by the optical wavelength multiplexer / demultiplexer. By forming corresponding to the, the output light output from each light output port,
A spectrum having a small background crosstalk centered on the light transmission center wavelength can be obtained.

That is, by forming an optical module by applying the optical wavelength band-pass filter of the present invention, the light is multiplexed or demultiplexed by an optical wavelength multiplexer / demultiplexer using a small number of optical wavelength band-pass filters. A plurality of lights can be collectively formed into a spectrum with a small background crosstalk centered on each light transmission center wavelength, and the total crosstalk can be reduced.

The optical wavelength band-pass filter of the present invention has a diffraction grating such as an arrayed waveguide type diffraction grating. Due to its characteristics, the light transmission center wavelength of one input / output port pair is set to the set wavelength. In the case where there is a deviation, if the deviation is compensated, the light transmission center wavelength of the other input / output port pairs can be adjusted to the set wavelength.

Therefore, even if the optical transmission center wavelength of the input / output port pair deviates from the set wavelength due to an error in the production of the optical wavelength band-pass filter or the like, the trouble of compensating for this deviation is eliminated by the optical wavelength multiplexer / demultiplexer. A bandpass / array waveguide type diffraction grating is connected to each output unit one by one, and the light transmission center wavelength of each bandpass / array waveguide type diffraction grating is significantly reduced as compared with the case where it is set to the set wavelength. be able to.

Therefore, an optical module formed by applying the optical wavelength band-pass filter of the present invention can be a small and low-cost optical module with small crosstalk.

[0066]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals are given to the same parts as those in the conventional example, and the overlapping description will be omitted. FIG. 1 shows a plan configuration of an optical module using an optical wavelength bandpass filter according to a first embodiment of the present invention.

As shown in the figure, the optical module of the present embodiment has a multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 as an optical wavelength multiplexing / demultiplexing device, and a characteristic light of the present embodiment. A wavelength band-pass filter 30. The optical wavelength band-pass filter 30 includes a plurality (eight in this case) of band-pass / array waveguide type diffraction gratings 9 (9a) as diffraction gratings.
To 9h).

Array / waveguide type diffraction grating 20 for multiplexing / demultiplexing
Has 40 optical output waveguides 26 and 100 GHz
It has a function of multiplexing and demultiplexing 40 light beams having different light transmission center wavelengths at intervals of about 0.8 nm. The frequency interval and the wavelength interval are intervals based on the ITU-T grid wavelength.

The multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 has 16 optical input waveguides 22. When the optical module of this embodiment is applied to wavelength division multiplexing communication, it is usually used. In FIG. 1, one optical input waveguide 22 is connected to an optical fiber or the like. Then, for example, 1 connected to an optical fiber or the like.
The wavelength-division multiplexed light is input to the two optical input waveguides 22, and is approximately 0.
The light is split into lights having different wavelengths at intervals of 8 nm, and output from the respective optical output waveguides 26.

As shown in FIG. 1, in the present embodiment, the band-pass / array waveguide type diffraction grating 9 constituting the optical wavelength band-pass filter 30 is the band-pass / array waveguide shown in FIG. Unlike the diffraction grating 9, a plurality (five in this example) of light input waveguides 12 are arranged at intervals from each other, and a plurality (five here) of optical output waveguides are arranged at intervals from each other. It has a waveguide 16 and, correspondingly, a plurality of optical input ports 2 and a plurality of optical output ports 6.

In FIG. 2, among the plurality of band-pass / array waveguide type diffraction gratings 9, the band-pass / array waveguide type diffraction grating 9 (9
a) and the coupling / demultiplexing / arrayed waveguide type diffraction grating 20 are shown, and as shown in FIG.
Through the multiplexing / demultiplexing / array waveguide type diffraction grating 20
One bandpass / arrayed waveguide type diffraction grating 9 (9a) is connected to the light output waveguide 26.

Similarly, the bandpass / array waveguide type diffraction grating 9 (9 b to 9 h) also receives five light beams of the multiplexing / demultiplexing / array waveguide type diffraction grating 20 via the optical fiber 3. The output waveguides 26 are connected one by one.

Each of the band-pass / array waveguide type diffraction gratings 9 outputs the light centered on the first light transmission center wavelength inputted from one light input port 2 from the corresponding light output port 6. Then, light centered on a second light transmission center wavelength different from the first light transmission center wavelength input from another light input port 2 is output from a corresponding light output port 6, for example. One optical input port 2 and one optical output port 6 are paired, and each input / output port pair transmits light having a wavelength centered on a different light transmission center wavelength.

For example, as shown in FIG. 3, the band-pass / array waveguide type diffraction grating 9 (9a) has a first light transmission center wavelength (λ) input from the first light input port 2a.
1) is output from the second optical output port 6b, which is the corresponding optical output port, and the second optical transmission center wavelength (λ2) input from the second optical input port 2b is output by the corresponding optical output port. The light is output from a certain fifth light output port 6e.

Further, the band-pass / array waveguide type diffraction grating 9 (9a) uses the third optical transmission center wavelength (λ3) input from the third optical input port 2c to output the corresponding optical output port. Output from a certain third optical output port 6c,
The fourth light transmission center wavelength (λ4) input from the optical input port 2d is output from the first optical output port 6a, which is the corresponding optical output port, and is input from the fifth optical input port 2e. The fifth light transmission center wavelength (λ5) is output from the corresponding light output port, that is, the fourth light output port 6d.

The other band-pass / array waveguide type diffraction grating 9 (9b to 9h) also has one optical input port 2
And one optical output port 6 as a pair, the respective input / output port pairs transmit light having wavelengths centered on different optical transmission center wavelengths. Further, the interval between the light transmission center wavelengths of the light transmitted by the plurality of input / output port pairs of the respective band-pass / array waveguide type diffraction gratings 9 (9a to 9h) (that is, the interval between adjacent light transmission center wavelengths). )
Are formed at substantially equal intervals.

For example, light transmission center wavelengths λ1, λ2, λ3, λ4, λ of light transmitted through the respective input / output port pairs of the band-pass / array waveguide type diffraction grating 9a.
As shown in FIG. 5, reference numerals 5 differ from each other by approximately equal intervals (Δλ), and the interval Δλ is 6.4 nm. That is, each of the band-pass / array waveguide type diffraction gratings 9 has a function of multiplexing / demultiplexing light having different wavelengths at intervals of 800 GHz (about 6.4 nm).

Incidentally, in the arrayed waveguide type diffraction grating, the above equation (1) indicates that all the wavelengths λ having different diffraction orders m
Holds, the light transmission center wavelength of the light output from one optical output waveguide is not one, but becomes, for example, a plurality of wavelengths as shown in FIG. FIG. 3 shows the transmitted light intensity (spectrum) transmitting the wavelengths corresponding to the diffraction orders M-1, M, and M + 1, and shows only three peaks. Appears by a number corresponding to all diffraction orders.

The difference between the peaks (center wavelengths of light transmission) between adjacent diffraction orders is expressed by the free spectral range (FSR; F
This is called a “spectrum range,” and is set by the design of an arrayed waveguide type diffraction grating. In this embodiment, the FSR is set to about 4000 GHz for each band-pass / array waveguide type diffraction grating.

Here, one band-pass / array waveguide type diffraction grating 9 (9a) will be described. For example, as shown in FIG. 7, the third light of the band-pass / array waveguide type diffraction grating 9a is obtained. From the input port 2c, light transmission center wavelengths λ1, λ2, λ3, which are different from each other at substantially equal intervals (Δλ).
When wavelength-division multiplexed lights of λ4 and λ5 are input, the band-pass / array waveguide type diffraction grating 9a demultiplexes the wavelength-division multiplexed light and outputs the respective light output ports 6 at the diffraction order M.
Lights having the light transmission center wavelengths λ5, λ4, λ3, λ2, and λ1 are output from a, 6b, 6c, 6d, and 6e, respectively.

When light is input from the third light input port 2c, the band-pass / arrayed waveguide type diffraction grating 9a has the light at the diffraction order M-1 as shown by the characteristic line e in FIG. Wavelength λ of light output from output port 6e
_A free spectral region is set so that _(M-1) is longer by Δλ than wavelength λ5 (so that the peak of characteristic line e at peak M-1 is Δ1 ').

That is, in this embodiment, the number of input / output port pairs of one band-pass / array waveguide type diffraction grating 9 is j (j = 5 in this embodiment), and a predetermined set integer. (I = 0 in the present embodiment), and when the diffraction order of the diffraction grating is M, the light transmission center wavelength of light transmitted by one set input / output port pair of the diffraction grating is λ.
_(M), and when the light transmission center wavelength of light transmitted through the set input / output port pair of the diffraction grating when the diffraction order of the diffraction grating is M-1, λ _(M-1) For the array waveguide type diffraction grating 9,
It is formed so that _(M−1) = λ _(M) + Δλ (i + j).

If this relationship is represented by a graph, the light input port 2c of the band-pass / array waveguide type diffraction grating 9a
FIG. 8 shows the spectrum of the light input from the optical output ports 6a to 6e and output from the optical output ports 6a to 6e.

In the figure, a characteristic line a indicates the spectrum of the light output from the light output port 6a, a characteristic line b indicates the spectrum of the light output from the light output port 6b, and a characteristic line c indicates the light. The spectrum of the light output from the output port 6c is shown.
, And the characteristic line e indicates the spectrum of the light output from the light output port 6e.

In the same figure, (peak M + 1)
Are the respective optical output ports 6a to 6e at the diffraction order M + 1.
(Peak M) is the spectrum of the light output from each of the optical output ports 6a to 6e at the diffraction order M, and (peak M-1) is the light output at the diffraction order M-1. The spectrum of the light output from the ports 6a to 6e is shown respectively.

Also, in the arrayed waveguide type diffraction grating,
The relationship of (Equation 1) is similarly established for the first slab waveguide. That is, as shown in FIG. 23, for example, if the focal center of the first slab waveguide 13 is a point O ′, and a point located at a position shifted from the point O ′ by a distance dx ′ in the X direction is a point P ′, When light is incident on this point P ′, the output wavelength is shifted by dλ ′. When this relationship is expressed by an equation, it becomes as shown in (Equation 3).

[0087]

(Equation 3)

In the equation (3), L _f ′ is the focal length of the first slab waveguide. This (Equation 3) is the first
By disposing the output end of the optical input waveguide at a position dx 'away from the focal point O' of the slab waveguide in the X direction, dλ 'in the optical output waveguide formed at the focal point O is obtained.
This means that light with different wavelengths can be extracted.

Therefore, based on (Equation 3), the output end interval of each optical input waveguide 12 is set, and
When wavelength-division multiplexed light having the light transmission center wavelengths λ1, λ2, λ3, λ4, and λ5 is incident from each of the optical input ports 2a to 2e, the wavelength demultiplexing characteristics are as shown in FIGS. become. When the wavelength demultiplexing characteristics when light is incident from each of the optical input ports 2a to 2e are shown by transmitted light intensity, (a) to (c) in FIG. 10 and (a) in FIG.
The result is as shown in FIG.

FIG. 10A shows the optical input port 2
The characteristic when light is incident from a, the characteristic when light is incident from the optical input port 2b is shown in (b) of the figure, and the characteristic when light is incident from the optical input port 2c is shown in (c) of the figure. FIG. 11A shows the characteristics when light enters from the optical input port 2d, and FIG. 11B shows the characteristics when light enters from the optical input port 2e.

Table 1 shows that the light transmission center wavelengths λ1, λ2, λ3, λ
4 shows the results obtained by summarizing the wavelength demultiplexing characteristics when light of λ5 is incident. In Table 1, those circled indicate the peak wavelength at the diffraction order M, those surrounded by squares indicate the peak wavelength at the diffraction order M + 1, and those without the circle indicate the peak wavelength at the diffraction order M-1. Is shown.

[0092]

[Table 1]

The optical input ports 2a to 2e shown in Table 1
And one of the light output ports 6a to 6e, one light input port 2 and one light output port such that the wavelength output from each of the output ports 6a to 6e does not overlap. When an input / output port pair consisting of 6 is set, the relationship is as shown in FIG.

That is, as described above, the band-pass / array waveguide type diffraction grating 9a is connected to the first optical input port 2a.
And the second light output port 6b as a pair, and the light transmission center wavelength λ
1, the second light input port 2b and the fifth light output port 6e are paired to transmit light having a light transmission center wavelength λ2, and the third light input port 2c and the third light output port 6c
, The light having the light transmission center wavelength λ3 is transmitted, the fourth light input port 2d and the first light output port 6a are transmitted as a pair, and the light having the light transmission center wavelength λ4 is transmitted.
e and the fourth light output port 6d as a pair, transmitting light having a light transmission center wavelength λ5.

In this embodiment, the sum (i + j) of the set integer i and the number j of the input / output port pairs in the relational expression λ _(M-1) = λ _(M) + Δλ (i + j) is an odd number ( Here, it is 5). Thus, by setting the sum of the set integer i and the input / output port pair j such that (i + j) becomes an odd number, as described above, each of the output ports 6a to 6
An input / output port pair including one optical input port 2 and one optical output port 6 can be set so that the wavelength output from e does not drop.

In this embodiment, the light transmission center wavelengths λ1, λ2, λ3, λ4, λ5 transmitted by the band-pass / array waveguide type diffraction grating 9 (9a) are as shown in FIG.
The light transmission center wavelength of light output from the first, ninth, seventeenth, twenty-fifth, and thirty-third optical output waveguides 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 shown in FIG. It is designed to be.

The light transmission band of the bandpass / array waveguide type diffraction grating 9 is wider than the light transmission band of the multiplexing / demultiplexing / array waveguide type diffraction grating 20. For example, the transmitted light intensity (spectrum) of light output from one optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is shown by a characteristic line a in FIG. The intensity of transmitted light that enters from one optical input port 2 of the band-pass / arrayed waveguide type diffraction grating 9 connected to the waveguide 26 and is output from the corresponding optical output port 6 (for one input / output port pair) The light transmission characteristic is formed so as to have the characteristic shown by the characteristic line b in FIG.

Then, the light is output from one optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 and connected to the optical output waveguide 26 for a bandpass / arrayed waveguide type diffraction grating. The spectrum of light incident from the light input port 2 of the grating 9 and output from the corresponding light output port 6 is as shown by a characteristic line c in FIG.

Since this effect is similarly exhibited in the other input / output port pairs of one band-pass / array waveguide type diffraction grating 9, in this embodiment, one band-pass / array waveguide is used. The waveguide type diffraction grating 9 collectively transmits five signal lights passing through the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 and can reduce the crosstalk of each signal light at a time.

In this embodiment, the same effect can be obtained for all the band-pass / array waveguide type diffraction gratings 9, so that each of the multiplexing / demultiplexing / array waveguide type diffraction gratings can be obtained. The light output from the optical output waveguide 26 and passed through the corresponding band-pass / array waveguide type diffraction grating 9 has a spectrum with a small background crosstalk centered on each light transmission center wavelength. Thus, the total crosstalk of the optical module can be reduced.

In this embodiment, as in the case where the optical waveguide circuit shown in FIG. 22 is applied, a bandpass is provided for each one optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20. Unlike the configuration in which the arrayed waveguide type diffraction grating 9 is connected, one bandpass is used for the five optical output waveguides 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20. Since the lattice 9 is connected, the manufacture of the optical module is facilitated, and the size of the optical module can be reduced.

Therefore, the optical module of the present embodiment can realize a small and low-cost optical module with small crosstalk.

In the optical module of the present embodiment, the optical wavelength band-pass filter 30 is used for a band-pass filter.
When the optical transmission center wavelength of one input / output port pair is deviated from the set wavelength for one band-pass / array waveguide type diffraction grating 9 and is configured to include the arrayed waveguide type diffraction grating 9, When the deviation is compensated, the light transmission center wavelength of the other input / output port pairs can be adjusted to the set wavelength.

Therefore, even if the light transmission center wavelength of the input / output port pair deviates from the set wavelength due to a manufacturing error of the band-pass / array waveguide type diffraction grating 9 constituting the optical wavelength band-pass filter 30, The trouble of compensating for this shift can be significantly reduced as compared with the case where the proposal example shown in FIG. 22 is applied.

FIG. 12 shows a second embodiment of the optical module according to the present invention. The second embodiment is substantially the same as the first embodiment, and the second embodiment is similar to the first embodiment.
The feature of the embodiment different from that of the first embodiment is that the wavelength multiplexing / demultiplexing number by the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is 8, and the optical wavelength bandpass filter 30 Is that the number of band-pass / array waveguide type diffraction gratings 9 that form is two.

Each band-pass / array waveguide type diffraction grating 9 has five light input ports 2 and five light output ports 6. Of which only four are used for multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20
Are connected to the optical output waveguide 26. That is, the second
In the embodiment, the number of input / output port pairs of each bandpass / array waveguide type diffraction grating 9 is four, and the number of input / output port pairs of the optical wavelength bandpass filter 30 is eight.

In the second embodiment, the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 is 400 GHz (about 3.2 GHz).
It has a function of multiplexing and demultiplexing eight light beams having different light transmission center wavelengths at intervals of (nm). On the other hand, the band-pass / array waveguide type diffraction grating 9 multiplexes and demultiplexes five lights having different light transmission center wavelengths at intervals of 800 GHz (about 6.4 nm) as in the first embodiment. Has a function.

That is, also in the second embodiment,
Δλ in band-pass / array waveguide type diffraction grating 9
Is about 6.4 nm, and in the second embodiment, the number j of the input / output port pairs is four, and the set integer i is one. Also in the second embodiment, the sum (i + j) of the set integer i and the number j of the input / output port pairs is an odd number (here, 5).
It is.

In the second embodiment, the light input port 2 of the band-pass / array waveguide type diffraction grating 9 (9a) is used.
a, light having a central wavelength of light transmission λ1 enters from the optical output port 6b, and is output from the optical input port 2b; light having a central wavelength of light transmission λ3 enters from the optical input port 2b, is output from the optical output port 6d; Light having a light transmission center wavelength λ5 is incident and output from the light output port 6c, and light having a light transmission center wavelength λ7 is input from the light input port 2d and output from the light output port 6a.

Also, light having a light transmission center wavelength λ2 enters from the light input port 2a of the band-pass array waveguide type diffraction grating 9 (9b), is output from the light output port 6b, and is output from the light input port 2b. Light having a transmission center wavelength λ4 is incident and output from the light output port 6d, light having a light transmission center wavelength λ6 is input from the light input port 2c and output from the light output port 6c, and light transmission center is transmitted from the light input port 2d. The light of wavelength λ8 enters and is output from the light output port 6a.

The second embodiment operates as described above, and the second embodiment can provide the same effects as those of the first embodiment.

FIG. 13 shows a third embodiment of the optical module according to the present invention. The third embodiment is substantially the same as the second embodiment, and the third embodiment is similar to the third embodiment.
The embodiment is different from the second embodiment in that the optical output waveguide 26 of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 and the light of the bandpass / arrayed waveguide type diffraction grating 9 are different. That is, the connection configuration with the input port 2 is different.

In the third embodiment, the same effect can be obtained by the same operation as that of the second embodiment.

Note that the present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example, in each of the above embodiments, the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 and the bandpass / arrayed waveguide type diffraction grating 9 are used.
The connection configuration is not limited to the above example, but may be set as appropriate. For example, based on the characteristics shown in Table 1, the wavelengths output from the output ports 6a to 6e are set so as not to be dull. An input / output port pair consisting of one optical input port 2 and one optical output port 6 may be set.

Further, in each of the above embodiments, the multiplexing / demultiplexing
The arrayed waveguide type diffraction grating 20 and the respective bandpass / arrayed waveguide type diffraction gratings 9 are formed on different substrates 1 from each other. For example, as shown in FIG. The diffraction grating 9 may be formed integrally on one substrate 1.

Further, as shown in FIG.
The arrayed waveguide type diffraction grating 20 and a plurality of bandpass / arrayed waveguide type diffraction gratings 9 may be integrated and formed on one substrate 1. In this case, the size of the optical module can be further reduced.

Further, the multiplexing / demultiplexing interval and the number of wavelengths of the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20 forming the optical module are not particularly limited, and are appropriately set.
In addition, the design of the band-pass / array waveguide type diffraction grating 9 is also based on the multiplexing / demultiplexing / array waveguide type diffraction grating 20 to be connected.
The above-mentioned relational expression λ _(M
-1) = λ _(M) + Δλ (i + j).

In the above relational expression, the sum (i + j) of the set integer i and the number j of the input / output port pairs is made to be an odd number, so that the band as applied to each of the above embodiments is obtained. Although the pass / array waveguide type diffraction grating 9 can be configured, if the set integer i is increased, the circuit configuration of the band-pass / array waveguide type diffraction grating 9 is increased, so the set integer i is 0 or 1. Is preferred.

Further, in each of the above embodiments, the optical wavelength band-pass filter 30 is formed by the band-pass / array waveguide type diffraction grating 9. However, the diffraction grating other than the band-pass / array waveguide type diffraction grating 9 is used. May be provided to form the optical wavelength bandpass filter 30.

Further, in each of the above embodiments, the optical wavelength multiplexer / demultiplexer forming the optical module is the multiplexing / demultiplexing / arrayed waveguide type diffraction grating 20, but the multiplexing / demultiplexing / arrayed waveguide type diffraction grating is used. An optical wavelength multiplexer / demultiplexer using a thin film filter, a bulk type diffraction grating, or the like other than the grating 20 can also be applied.

Further, in the present invention, the light transmission center wavelength in the optical wavelength band-pass filter is usually set to
The grid wavelength is adjusted to the U-T grid wavelength, and since the grid wavelength is a frequency unit at intervals of 100 GHz, it is not exactly equal in wavelength unit.
For this reason, the design of the optical wavelength band-pass filter such as the band-pass / array waveguide type diffraction grating can also adjust the wavelength interval according to the grid wavelength (intentionally make the interval not equal). .

Even when this adjustment is not performed, the deviation between the central wavelength of light transmission and the grid wavelength is small compared to the transmission band of an optical wavelength band-pass filter such as a band-pass / array waveguide type diffraction grating. It does not hinder the effects of the present invention. Further, even when the wavelength interval is adjusted, a shift between the light transmission center wavelength and the grid wavelength occurs with respect to peaks for different diffraction orders, but the shift amount is also small, and the effect of the present invention is also small. It does not hinder.

[0123]

According to the optical wavelength bandpass filter of the present invention, the optical transmission center wavelength of the light transmitted through each of the plurality of input / output port pairs can be adjusted by the optical wavelength combining such as a multiplexing / demultiplexing / arrayed waveguide type diffraction grating. By forming the light corresponding to the light transmission center wavelength of the light to be multiplexed / demultiplexed by the demultiplexer, the output lights output from the respective light output ports are collectively collected, and the back light is centered on the light transmission center wavelength. A spectrum with small ground crosstalk can be obtained.

Therefore, by forming the optical module by applying the optical wavelength band pass filter of the present invention,
Using a small number of optical wavelength band-pass filters, convert multiple light beams that are split or multiplexed by an optical wavelength multiplexer / demultiplexer into a spectrum with a small background crosstalk centered on each light transmission center wavelength. Thus, the total crosstalk of the optical module can be reduced and the size can be reduced.

Further, in the optical wavelength band-pass filter of the present invention, if the intervals of the light transmission center wavelengths of the light transmitted through the plurality of input / output port pairs are made substantially equal, the design becomes easy, and When forming an optical module for wavelength multiplexing communication, the optical wavelength bandpass filter of the present invention can be easily applied.

Further, in the optical wavelength bandpass filter of the present invention, the interval between the light transmission center wavelengths of the light transmitted through the plurality of input / output port pairs, the number of the input / output port pairs, the set integer, and the diffraction order of the diffraction grating. Is M, the light transmission center wavelength of the light transmitted by one set input / output port pair of the diffraction grating, and transmitted by the set input / output port pair of the diffraction grating when the diffraction order of the diffraction grating is M-1. According to the third aspect of the invention in which the relationship between the light transmission center wavelengths is determined, it is possible to easily and accurately form an optical wavelength bandpass filter capable of exerting the above-described effects.

Further, in the optical wavelength bandpass filter of the present invention, according to the configuration in which the set integer i is set to 0,
A compact optical wavelength bandpass filter can be formed.

Further, in the optical wavelength band-pass filter of the present invention, according to the configuration in which the sum (i + j) of the set integer i and the number j of input / output port pairs is an odd number, the above-mentioned configuration can be easily and accurately performed. It is possible to form an optical wavelength bandpass filter capable of exhibiting an effect.

Further, in the optical wavelength bandpass filter of the present invention, according to the present invention, wherein the diffraction grating is an arrayed waveguide type diffraction grating, the wavelength of light transmitted through a plurality of optical input port pairs is set accurately. Even if the light transmission center wavelength of the input / output port pair deviates from the set wavelength, if the light transmission center wavelength of one input / output port pair is compensated for, the other input / output port pairs will also be compensated. The light transmission center wavelength can be adjusted to the set wavelength.

Therefore, even if the optical transmission center wavelength of the input / output port pair deviates from the set wavelength due to an error in the production of the optical wavelength band-pass filter or the like, the trouble of compensating for this deviation is eliminated by the optical wavelength multiplexer / demultiplexer. A bandpass / array waveguide type diffraction grating is connected to the output unit one by one, and the light transmission center wavelength of each bandpass / array waveguide type diffraction grating is significantly reduced as compared with the case where it is set to the set wavelength. As a result, downsizing and cost reduction of the optical module can be realized more reliably.

Further, in the optical wavelength bandpass filter of the present invention, according to the configuration in which a plurality of diffraction gratings are formed, it is easy to increase the number of input / output port pairs in the entire optical wavelength bandpass filter. You can do much.

Further, according to the optical module of the present invention,
By providing an optical module including the above-mentioned optical wavelength bandpass filter and the corresponding optical wavelength multiplexer / demultiplexer,
It is possible to realize a small-sized and low-cost optical module capable of multiplexing / demultiplexing light having a wavelength to be multiplexed / demultiplexed by the optical wavelength multiplexer / demultiplexer with low crosstalk.

Further, in the optical module of the present invention,
According to the configuration in which the optical wavelength multiplexer / demultiplexer and the optical wavelength bandpass filter are formed on the same substrate, it is possible to further reduce the size of the optical module.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of an optical module according to the present invention.

FIG. 2 is an explanatory diagram showing a connection configuration between a multiplexing / demultiplexing / arrayed waveguide type diffraction grating and one bandpass / arrayed waveguide type diffraction grating in the embodiment.

FIG. 3 is an explanatory diagram showing a wavelength transmission operation of one band-pass / array waveguide type diffraction grating applied to the embodiment.

FIG. 4 shows an example of optical transmission characteristics of the optical module of the embodiment, the multiplexing / demultiplexing / array waveguide type diffraction grating, and the bandpass / array waveguide type diffraction grating applied to the optical module. It is a graph shown.

FIG. 5 is a graph showing an example of wavelengths that are passed by one band-pass / array waveguide type diffraction grating applied to the embodiment.

FIG. 6 shows light transmission wavelength and F when diffraction orders are different from each other.
It is a graph which shows the relationship with SR.

FIG. 7 is an explanatory diagram showing an operation when wavelength-division multiplexed light is input to a third optical input port of one band-pass / array waveguide type diffraction grating applied to the embodiment.

FIG. 8 shows light output from each optical output port when wavelength-division multiplexed light is input to the third optical input port of one band-pass / arrayed waveguide type diffraction grating applied to the embodiment. 5 is a graph showing the wavelength characteristics of FIG.

FIG. 9 is an explanatory diagram showing an operation when wavelength-division multiplexed light is input to each optical input port of one band-pass / array waveguide type diffraction grating applied to the embodiment.

FIG. 10 shows an output from each optical output port when wavelength-division multiplexed light is input to the first to third optical input ports of one band-pass / array waveguide type diffraction grating applied to the embodiment. 4 is a graph showing wavelength characteristics of light to be emitted.

FIG. 11 shows an output from each optical output port when wavelength-division multiplexed light is input to fourth and fifth optical input ports of one band-pass / arrayed waveguide type diffraction grating applied to the embodiment. 4 is a graph showing wavelength characteristics of light to be emitted.

FIG. 12 is a main part configuration diagram showing a second embodiment of the optical module according to the present invention.

FIG. 13 is a main part configuration diagram showing a third embodiment of the optical module according to the present invention.

FIG. 14 is an explanatory diagram showing another example of the optical wavelength bandpass filter according to the present invention.

FIG. 15 is a main part configuration diagram showing another embodiment of the optical module according to the present invention.

FIG. 16 is an explanatory diagram showing a configuration and an optical demultiplexing operation of an arrayed waveguide grating.

FIG. 17 is a graph showing an example of light transmission characteristics of an arrayed waveguide grating.

FIG. 18 is a graph collectively showing light transmission characteristics of each light output from each light output waveguide of the arrayed waveguide grating.

FIG. 19 is an illustration showing the configuration of an arrayed waveguide diffraction grating together with a wavelength multiplexing operation.

FIG. 20 is a graph for explaining the concept of background crosstalk.

FIG. 21 is an explanatory diagram showing an example of an optical module using a conventional multiplexing / demultiplexing / arrayed waveguide type diffraction grating.

FIG. 22 is an explanatory view showing an optical waveguide circuit of an arrayed waveguide type diffraction grating provided with one optical input waveguide and one optical output waveguide, proposed for use as a bandpass filter.

FIG. 23 is an explanatory diagram showing a relationship between a light transmission center wavelength shift and positions of an optical input waveguide and an optical output waveguide in an arrayed waveguide type diffraction grating.

FIG. 24 is a graph showing an example of light transmission characteristics of each of a multi / demultiplexing / arrayed waveguide type diffraction grating, a bandpass / arrayed waveguide type diffraction grating, and an optical module in which these are combined.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2, 2a-2e Optical input port 3 Optical fiber 6, 6a-6e Optical output port 9, 9a-9h Band-pass / array waveguide type diffraction grating 10 Waveguide formation area 12, 22 Optical input waveguide 13, 23 First Slab Waveguide 14, 24 Array Waveguide 15, 25 Second Slab Waveguide 16, 26 Optical Output Waveguide 20 Array Waveguide Diffraction Grating for Demultiplexing / Demultiplexing 30 Optical Wavelength Bandpass Filter

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Kawashima 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 2H047 KA03 KA12 LA01 LA19 RA00 TA23 2H049 AA59 AA62 AA65

Claims (9)

[Claims] A diffraction grating; a plurality of light input ports for inputting light to the diffraction grating; and a plurality of light output ports for outputting light passing through the diffraction grating. A second light different from the first light transmission center wavelength inputted from another light input port is outputted from a corresponding light output port, with the light having the inputted first light transmission center wavelength as a center. One light input port and one light output port are paired so that different light transmission center wavelengths are centered on each input / output port pair, such that light centered on the transmission center wavelength is output from the corresponding light output port. An optical wavelength bandpass filter, which transmits light having a wavelength defined as follows. 2. The optical wavelength band-pass filter according to claim 1, wherein the intervals between the light transmission center wavelengths of the light transmitted through the plurality of input / output port pairs are substantially equal. 3. A diffraction grating when the interval between light transmission center wavelengths of light transmitted by a plurality of input / output port pairs is Δλ, the number of the input / output port pairs is j, and the diffraction order of the diffraction grating is M. The light transmission center wavelength of the light transmitted through one of the set input / output port pairs is λ _(M), and the light transmitted through the set input / output port pair of the diffraction grating when the diffraction order of the diffraction grating is M−1. Λ
_(M-1), and when a predetermined set integer is i,
3. The optical wavelength bandpass filter according to claim 2, wherein λ _(M-1) = λ _(M) + Δλ (i + j). 4. The optical wavelength band-pass filter according to claim 3, wherein the set integer i is set to 0. 5. The optical wavelength band-pass filter according to claim 3, wherein the sum (i + j) of the set integer i and the number j of the input / output port pairs is an odd number. 6. A diffraction grating comprising: one or more optical input waveguides arranged side by side; and a first optical waveguide connected to an output side of the optical input waveguide.
A slab waveguide, an array waveguide connected to the output side of the first slab waveguide, a second slab waveguide connected to the output side of the array waveguide, and the second slab waveguide. A plurality of juxtaposed optical output waveguides connected to the output side of the waveguide, wherein the arrayed waveguides have respective lengths for propagating light derived from the first slab waveguide. The optical wavelength bandpass filter according to any one of claims 1 to 5, wherein an arrayed waveguide type diffraction grating is provided in which a plurality of channel waveguides having different amounts are arranged in parallel. 7. The optical wavelength band pass according to claim 1, wherein a plurality of diffraction gratings are provided, and the plurality of diffraction gratings are formed on the same substrate. filter. 8. An optical wavelength bandpass filter according to claim 1, wherein the optical wavelength bandpass filter corresponds to a wavelength of light transmitted by each of a plurality of input / output port pairs of the optical wavelength bandpass filter. An optical wavelength multiplexer / demultiplexer for multiplexing / demultiplexing light having a wavelength. 9. The optical module according to claim 8, wherein the optical wavelength bandpass filter and the optical wavelength multiplexer / demultiplexer are formed on the same substrate.