Patent Publication Number: US-2004047558-A1

Title: Optical module

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to an optical module that includes an optical fiber array and a lens array, and is formed as a collimator or a collimator array.  
       [0002] Such an optical module is used in an optical communication field as a collimator optical device by using a pair of the optical modules. In the collimator optical device, an optical function element, such as an optical filter, an optical isolator, an optical switch, and an optical modulator, is inserted between the pair of the above mentioned optical modules. The collimator optical device applies a predetermined effect on light that is transmitted through an optical fiber on an incoming side, and couples the light to an optical fiber on an outgoing side.  
       [0003] In the prior art, an optical module has been proposed as shown in FIGS. 8 and 9. The optical module is formed as a collimator array and includes an optical fiber array  21 , which retains optical fibers  20  arranged in a line, and a lens array  23 , which includes microlenses  22  arranged in a line. (For example, Japanese Laid-Open Patent Publication 2001-305376). The optical fiber array  21  has a capillary  24 , which retains the optical fibers  20  as a unit. The lens array  23  is a flat microlens array that has a transparent lens substrate  25 . The microlenses  22  are formed on the right end surface of the lens substrate  25 . The positions of the optical fiber array  21  and the lens array  23  are determined such that the distance between a fiber outgoing end surface  26  and the microlenses  22  is substantially equal to a focal distance f of the microlenses  22 , which is a predetermined lens to optical fiber distance L.  
       [0004] An optical module shown in FIGS. 10 and 11 is substantially the same as the optical module shown in FIGS. 8 and 9 except that the surface of the lens substrate  25  on which the microlenses  22  are arranged faces the fiber outgoing end surface  26 . In the optical module shown in FIGS. 10 and 11, the positions of the optical fiber array  21  and the lens array  23  are determined such that the distance between the fiber outgoing end surface  26  and the microlenses  22  is equal to the predetermined lens to optical fiber distance L.  
       [0005]FIG. 12 shows a conventional optical module that includes a single core capillary  32 , which retains an optical fiber  31 , and a gradient index rod lens  33 . The optical module of FIG. 12 is formed as a collimator (single collimator). In the optical module shown in FIG. 12, a fiber outgoing end surface  34  and a lens incoming end surface  35  of the rod lens  33  are polished to have the same inclination angle in order to reduce reflected return light at the fiber outgoing end surface  34  and the lens incoming end surface  35 . Such an optical module has been proposed in, for example, Japanese Laid-Open Patent Publication No. 2002-196182. In such an optical module, it has been proposed to reduce the reflected return light at a lens outgoing end surface  36  of the rod lens  33  by tilting an outgoing light from the rod lens  33  with respect to an optical axis of the rod lens  33 . The reflected return light refers to light that is reflected by the fiber outgoing end surface  34  of the optical fiber  31 , the lens incoming end surface  35  of the rod lens  33 , and the lens outgoing end surface  36 , and that returns to the optical fiber  31  on the incoming side  
       [0006] In the optical module shown in FIGS. 8 and 9, the reflected return light is generated at the fiber outgoing end surface  26 , the lens incoming end surface  27  of the lens substrate  25 , and the lens outgoing end surface  28  of the lens substrate  25 . Further, in the optical module shown in FIGS. 8 and 9, the capillary  24  and the lens substrate  25  are rectangular. This increases the reflected return light. If the reflected return light that occurs at the above mentioned three surfaces returns to a light source, such as a semiconductor laser, through the optical fibers  20  on the incoming side, the oscillation of the semiconductor laser becomes unstable. Therefore, it is required to minimize the reflected return light of each optical module. When similar optical modules are arranged in multiple stages, the reflected return light caused in each optical module increases as the number of stages of the optical modules is increased. Thus, the necessity to reduce the reflected return light is further increased.  
       [0007] In the optical module shown in FIGS. 10 and 11, the reflected return light is also caused at the fiber outgoing end surface  26 , a lens incoming end surface  29  of the lens substrate  25 , and a lens outgoing end surface  30  of the lens substrate  25 . Therefore, in the optical module of FIGS. 10 and 11, it is also required to minimize the reflected return light of each optical module.  
       [0008] In the optical module shown in FIG. 12, when the outgoing light from the rod lens  33  is tilted with respect to the optical axis of the rod lens  33  to reduce the reflected return light at the lens outgoing end surface  36 , the following problems might be caused. Since the outgoing light from the rod lens  33  is tilted with respect to the optical axis, a similar optical module or another optical part needs to be attached to the optical module at an angle. This increases the number of parts and takes a lot of trouble in the adjustment for mounting the similar optical module or another optical part. Further, if the outgoing light is tilted with respect to the optical axis at a large angle, a large space is required for arranging another optical part.  
       SUMMARY OF THE INVENTION  
       [0009] Accordingly, it is an objective of the present invention to provide an optical module that reduces reflected return light. Another objective of the present invention is to provide an optical module that reduces reflected return light while reducing number of parts, procedures for adjustment, and a space required for mounting, for example, optical parts.  
       [0010] To achieve the above objective, the present invention provides an optical module, which includes an optical fiber array and a lens array. The optical fiber array has at least one optical fiber and an outgoing end surface. The optical fiber includes a central axis of the optical fiber. The lens array has at least one microlens. The lens array includes an incoming end surface, which faces the outgoing end surface of the optical fiber array, and an outgoing end surface, which sends out a light that is transmitted through the microlens. The microlens has an optical axis. The outgoing end surface of the optical fiber array is formed to be inclined with respect to the central axis of the optical fiber. The incoming end surface of the lens array is formed to be inclined with respect to the optical axis of the microlens. The relative position of the optical fiber array and the lens array is adjusted such that an inclination angle of the outgoing light sent out from the outgoing end surface of the lens array with respect to the optical axis of the microlens becomes an optimal angle.  
       [0011] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012] The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
     [0013]FIG. 1 is a side view illustrating an optical module according to a first embodiment of the present invention;  
     [0014]FIG. 2 is a plan view illustrating the optical module shown in FIG. 1;  
     [0015]FIG. 3 is a side view illustrating an optical system used in a simulation;  
     [0016]FIG. 4 is a graph showing a result of the simulation;  
     [0017]FIG. 5 is a side view illustrating an optical module according to a second embodiment;  
     [0018]FIG. 6 is a side view illustrating an optical module according to a third embodiment;  
     [0019]FIG. 7 is a side view illustrating an optical module according to a fourth embodiment;  
     [0020]FIG. 8 is a plan view illustrating a prior art optical module;  
     [0021]FIG. 9 is a side view illustrating the optical module shown in FIG. 8;  
     [0022]FIG. 10 is a plan view illustrating another prior art optical module;  
     [0023]FIG. 11 is a side view illustrating the optical module shown in FIG. 10; and  
     [0024]FIG. 12 is a side view illustrating another prior art optical module.  
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0025] An optical module according to embodiments of the present invention will be described with reference to drawings.  
     [0026]FIGS. 1 and 2 show an optical module  40  according to a first embodiment. The optical module  40  includes an optical fiber array  42 , which has optical fibers (single mode optical fibers)  41 , and a lens array  44 , which has microlenses, which are microlenses  43  in the first embodiment. The optical module  40  is formed as a collimator array.  
     [0027] The optical fiber array  42  has a capillary  45 , which retains optical fibers  41  as a unit. The lens array  44  is a flat microlens array that has a transparent lens substrate  46 . The microlenses  43  are formed on a right end surface  46   a  (first end surface) of the lens substrate  46 . The lens array  44  is arranged such that a left end surface  46   b  (second end surface) of the lens substrate  46  faces a fiber outgoing end surface  46   a  of the optical fiber array  42 .  
     [0028] In the optical module  40 , the fiber outgoing end surface  46   a  is polished to be inclined with respect to a central axis C 2  of a core of the optical fiber  41 . The left end surface  46   b  of the lens substrate  46  (a lens incoming end surface of the lens array  44 ) that faces the fiber outgoing end surface  46   a  is polished to be inclined with respect to an optical axis C 1  of each microlens  43 . The right end surface  46   a  of the lens substrate  46  is polished to be perpendicular to the optical axis C 1  of the microlenses. The optical fiber array  42  and the lens array  44  are adjusted such that an angle α between an outgoing light A sent out from a lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46  in the first embodiment, and the optical axis C 1  of the microlenses is optimal. Assume that when the outgoing light A is inclined lower than the optical axis C 1  of the microlenses, the angle between the outgoing light A and the optical axis C 1  is expressed by a negative value (−). In this case, the optimal angle is, for example, −0.84 degrees.  
     [0029] In the optical module  40 , the fiber outgoing end surface  46   a,  the lens incoming end surface of the lens array  44 , which is the left end surface  46   b  of the lens substrate  46 , and the lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46 , are inclined with respect to the central axis C 2  of the core of the optical fiber  41 .  
     [0030] That is, the inclination angle between the fiber outgoing end surface  46   a  and a surface that is perpendicular to the central axis C 2  of the optical fiber differs from the inclination angle between the left end surface  46   b  of the lens substrate  46  and a surface that is perpendicular to the optical axis C 1  of the microlenses by an absolute value (0.84 degrees) of the optimal angle. Since the left end surface  46   b  faces the fiber outgoing end surface  46   a  in parallel, the fiber outgoing end surface  46   a,  the left end surface  46   b,  and the right end surface  46   a  are all inclined with respect to the central axis C 2  of the optical fiber. The lens array  44  is shifted in parallel with the fiber outgoing end surface  46   a,  or in a direction represented by an arrow DD′ in FIG. 1, such that the outgoing light A becomes parallel with the central axis C 2  of the optical fiber. In the first embodiment, the lens array  44  is shifted in parallel with the fiber outgoing end surface  46   a  such that the outgoing light A becomes horizontal as viewed in FIG. 1. To check if the outgoing light A is horizontal, for example, an infrared sensor card, the color of which changes when an infrared light is irradiated, is used to measure the outgoing light A at two points at the same height. The inclination angle α of the outgoing light A with respect to the optical axis C 1  of the microlenses will hereafter be referred to as a beam tilt angle.  
     [0031] In the first embodiment, the optimal angle of the beam tilt angle α is set to −0.84 degrees. The fiber outgoing end surface  46   a  of the optical fiber array  42  is polished to be inclined with respect to a surface that is perpendicular to the central axis C 2  of the optical fiber by 8 degrees. The lens incoming end surface, which is the left end surface  46   b  of the lens substrate  46 , is polished to be inclined with respect to a surface that is perpendicular to the optical axis C 1  of the microlenses by 8.84 degrees.  
     [0032] The first embodiment provides the following advantages.  
     [0033] (a) The fiber outgoing end surface  46   a  and the lens incoming end surface, which is the left end surface  46   b  of the lens substrate  46 , are each polished such that the fiber outgoing end surface  46   a  is inclined with respect to the central axis C 2  of the optical fiber, and the left end surface  46   b  is inclined with respect to the optical axis C 1  of the microlenses. The inclination angle of the fiber outgoing end surface  46   a  relative to central axis C 2  and the inclination angle of left end surface  46   b  relative to optical axis C 1  are different by 0.84 degrees. Since the left end surface  46   b  of the lens substrate  46  faces the fiber outgoing end surface  46   a  in parallel, the fiber outgoing end surface  46   a,  the left end surface  46   b,  and the right end surface  46   a  are all inclined with respect to the central axis C 2  of the optical fiber. Accordingly, the reflected return light at the three surfaces are reduced. Therefore, the outgoing light A need not be inclined with respect to the central axis C 2  of the optical fiber in order to reduce reflected return light at the lens outgoing end surface in the manner as the above mentioned prior art. Also, increase of an insertion loss caused by excessively tilting the outgoing light A with respect to the optical axis C 1  of the microlenses is prevented.  
     [0034] (b) The insertion loss is decreased by adjusting the optical fiber array  42  and the lens array  44  such that the angle between the outgoing light A and the optical axis C 1  of the microlenses (the beam tilt angle α) becomes the optimal angle (−0.84 degrees).  
     [0035] (c) The optical fiber array  42  and the lens array  44  are adjusted such that the outgoing light A becomes parallel with the central axis C 2  of the optical fiber. Accordingly, the number of parts, adjusting procedures, and a space for mounting another optical part are reduced. Therefore, the optical module  40  reduces the reflected return light while reducing the number of parts, adjusting procedures, and a space for mounting another optical part, and reducing the insertion loss.  
     [0036] In an optical system shown in FIG. 3, an outgoing light from each optical fiber  41  is converted into a parallel beam by a corresponding one of microlenses  43 ′ of a lens array (flat microlens)  44 ′. The parallel beam then enters a mirror  50  and is reflected by the mirror  50 . The reflected light is converged by the lens array  44 ′ and enters another optical fiber  41 . In this case, the insertion loss (IL) is represented by the following equation.  
     Insertion Loss ( dB )=10×Log (Incoming light Amount Pout/Outgoing light Pin)  
     [0037] (d) The lens array  44  is shifted parallel to the fiber outgoing end surface  46   a,  or in the DD′ direction, such that the outgoing light A becomes parallel with the central axis C 2  of the optical fiber. That is, when the lens array  44  is shifted with respect to the optical fiber array  42  parallel to the fiber outgoing end surface  46   a,  or in the DD′ direction, the outgoing angle of the outgoing light A is varied. The position where the outgoing light A becomes parallel with the central axis C 2  of the optical fiber is the optimal position of the lens array  44 . This facilitates adjusting of the position of the lens array  44  with respect to the optical fiber array  42 .  
     [0038] (e) In the optical module  40  that uses a flat microlens as the lens array  44 , the reflected return light is reduced while reducing the number of parts, the adjusting procedures, and a space for mounting another optical part, and reducing the insertion loss.  
     [0039] (f) The beam tilt angle α is adjusted to be the optimal angle of −0.84 degrees. Therefore, the insertion loss is minimized, and the reflected return light is also minimized.  
     [0040] The beam tilt angle α, or the inclination angle of the outgoing light A with respect to the optical axis C 1  of the microlenses, is changed, and the insertion loss and a return loss of each beam tilt angle α is calculated in the following simulation. As a result, the optimal result is obtained when the beam tilt angle is set to −0.84 degrees. That is, the insertion loss is minimum and the return loss is maximum (reflection return light is minimum) when the beam tilt angle is set to −0.84 degrees. The return loss (RL) is represented by the following equation.  
     Return loss ( dB )=−10×Log (Outgoing Light Amount Pin/Amount Of Reflected Return Light P′ in)  
     [0041] In the above equation, Pin represents the outgoing light amount sent out from the optical fiber  41 , P′ in represents the amount of reflected return light returned to the optical fiber  41  after being reflected by the above mentioned three surfaces.  
     [0042] The simulation was performed using the optical system shown in FIG. 3 under the following conditions with the following calculation method.  
     [0043] Conditions  
     [0044] (1) The numerical aperture of the optical fiber  41  was 0.10 (wave length: 1550 nm), and the inclination angle of the fiber outgoing end surface  46   a  was 8 degrees.  
     [0045] (2) The refractive index n of a lens substrate  46 ′ of the flat microlens array (lens array  44 ′) was 1.523, the thickness Z of the lens substrate  46 ′ on the light path was approximately 1 mm, the working distance WD was 0.100 (mm), the inclination angle of a lens incoming end surface  46   b ′ was 8 degrees, and the lens diameter of each microlens  43 ′ was 250 μm.  
     [0046] Calculation Method  
     [0047] (1) In the optical system shown in FIG. 3, the distance L between the lens array  44 ′ and the mirror  50  was 1 mm. The offset amount (SMF-offset(Y)(mm)) of the optical fiber  41  with respect to the optical axis C 1  of the microlenses and the inclination angle (Mirror-tilt(degree)) of the mirror  50  with respect to the optical axis C 1  of the microlenses were adjusted such that the insertion loss (IL(dB)) was minimized. Then, the insertion loss was calculated. The inclination angle of the mirror  50  was adjusted only when calculating the insertion loss.  
     [0048] (2) In a state where the insertion loss calculated as described above was optimal, the amount of the reflected return light (P′ in) from a lens outgoing end surface  46   a ′ of the lens substrate  46 ′ to the optical fiber  41  was calculated. The return loss (RL(dB)) was then calculated using the above equation. An antireflection film was formed on the lens outgoing end surface  46   a ′. The reflectivity of the lens outgoing end surface  46   a ′ was 0.2%.  
     [0049] (3) The beam tilt angle α, or the inclination of the outgoing light A from the lens incoming end surface  46   b ′ with respect to the optical axis C 1  of the microlenses was varied, and the calculations (1) and (2) are repeatedly performed on each beam tilt angle α to obtain the insertion loss and the return loss. The result is shown in the following Table 1 and a graph of FIG. 4.  
                                       TABLE 1                       SMF-offset (Y)   Beam Tilt   WD   IL   Mirror-tilt   RL           (mm)   Angle (°)   (mm)   (dB)   (°)   (dB)                                                            −0.019   1.05   0.069   0.67   1.05   71.7           −0.012   0.49   0.070   0.48   0.49   47.1       −0.010   0.34   0.071   0.38   0.34   39.0       −0.006   0.00   0.071   0.31   0.00   27.5       0.000   −0.45   0.072   0.23   −0.45   47.4       0.004   −0.74   0.073   0.22   −0.74   64.5       0.005   −0.84   0.073   0.22   −0.84   84.8      Best       0.008   −1.07   0.073   0.25   −1.07   76.5    Position       0.013   −1.46   0.073   0.30   −1.46   79.4       0.019   −1.93   0.073   0.44   −1.93   79.3       0.026   −2.47   0.073   0.66   −2.47   78.7                  
 
     [0050] As a result of the above simulation, as shown in Table 1 and FIG. 4, when the beam tilt angle α is −0.84, the insertion loss is minimum and the return loss is maximum (the reflected return light is minimum).  
     [0051]FIG. 5 shows an optical module  40 A according to a second embodiment. The optical module  40 A includes the lens array  44 , which is formed by a flat microlens array. The left end surface  46   b  of the lens substrate  46  of the lens array  44  faces the fiber outgoing end surface  46   a.  The fiber outgoing end surface  46   a  and the right end surface  46   a  of the lens substrate  46  are polished to be inclined with respect to the axes C 2  and C 1 , respectively, at different angles. The inclination angle of the optical axis C 1  of the microlenses with respect to the central axis C 2  of the optical fiber is adjusted such that the outgoing light A from the right end surface  46   a  of the lens substrate  46  becomes parallel with the central axis C 2  of the optical fiber, or such that the outgoing light A from the right end surface  46   a  of the lens substrate  46  becomes horizontal as viewed in FIG. 5. That is, when the lens array  44  is shifted with respect to the optical fiber array  42  in parallel with the fiber outgoing end surface  46   a,  the outgoing angle of the outgoing light A varies. The position where the outgoing light A becomes parallel with the central axis C 2  of the optical fiber is the optimal position of the lens array  44 . To check whether the outgoing light A is horizontal, an infrared sensor is used to measure the outgoing light A at two points at the same height in the same manner as the first embodiment.  
     [0052] In the second embodiment, for example, the fiber outgoing end surface  46   a  is polished to be inclined with respect to a surface that is perpendicular to the central axis C 2  of the optical fiber by 8 degrees. The lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46  is polished to be inclined with respect to a surface that is perpendicular to the optical axis C 1  of the microlenses by 1.46 degrees. The lens incoming end surface, which is the left end surface  46   b  of the lens substrate  46 , is inclined with respect to a surface that is perpendicular to the central axis C 2  of the optical fiber by 2.78 degrees. The lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46 , is inclined with respect to a surface that is perpendicular to the central axis C 2  of the optical fiber by 4.24 degrees. Accordingly, the left end surface  46   b  of the lens substrate  46  faces the fiber outgoing end surface  46   a  at a predetermined angle. Thus, the three surfaces are inclined with respect to the central axis C 2  of the optical fiber. Therefore, the angle between a beam B and the central axis C 2  of the optical fiber is 3.78 degrees, the angle between a beam C and the central axis C 2  of the optical fiber is 2.78 degrees, and the angle between a beam (outgoing light) A and the central axis C 2  of the optical fiber is zero degrees.  
     [0053] The second embodiment provides the following advantages.  
     [0054] (g) The fiber outgoing end surface  46   a  and the lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46  are polished at different angles, and the lens incoming end surface, which is the left end surface  46   b  of the lens substrate  46  is polished to be perpendicular to the optical axis C 1  of the microlenses. The left end surface  46   b  faces the fiber outgoing end surface  46   a  at the predetermined angle. Therefore, the three surfaces  46   a,    46   a,  and  46   b  are inclined with respect to the central axis C 2  of the optical fiber. Accordingly, the reflection return light at each surface  46   a,    46   a,  or  46   b  is reduced.  
     [0055] (h) The lens array  44  is shifted in parallel with the fiber outgoing end surface  46   a  such that the outgoing light A becomes parallel with the central axis C 2  of the optical fiber. This facilitates adjusting of the lens array  44  with respect to the optical fiber array  42 .  
     [0056] (i) The lens array  44  is shifted with respect to the optical fiber array  42  in parallel with the fiber outgoing end surface  46   a  such that the outgoing light A becomes parallel with the central axis C 2  of the optical fiber. This varies the outgoing angle of the outgoing light A. Accordingly, the lens array  44  is adjusted to the optimal position where the outgoing light A becomes parallel with the central axis C 2  of the optical fiber.  
     [0057] (j) The flat microlens array (lens array  44 ) is arranged such that the left end surface  46   b  of the lens substrate  46  faces the fiber outgoing end surface  46   a.  Therefore, the reflected return light is reduced while reducing the number of parts, adjusting procedures, and a space for mounting another optical part and reducing the insertion loss.  
     [0058]FIG. 6 shows an optical module  40 B according to a third embodiment. The optical module  40 B includes the optical fiber array  42  and the lens array  44  in the same manner as the first embodiment shown in FIGS. 1 and 2.  
     [0059] In the optical module  40 B, the fiber outgoing end surface  46   a  and the lens incoming end surface, which is the left end surface  46   b  of the lens substrate  46 , are polished to be inclined with respect to the central axis C 2  of the optical fiber at the same angle. The left end surface  46   b  faces the fiber outgoing end surface  46   a  in parallel. The angle (beam tilt angle α) of the outgoing light A with respect to the optical axis C 1  of the microlenses is adjusted to the optimal angle (−0.84 degrees) by shifting the lens array  44  in parallel with the fiber outgoing end surface  46   a.    
     [0060] The third embodiment provides the following advantages.  
     [0061] (k) The reflection return light at the fiber outgoing end surface  46   a  and the left end surface  46   b  is reduced.  
     [0062] (l) The beam tilt angle α is adjusted to the optimal angle by shifting the lens array  44  in parallel with the fiber outgoing end surface  46   a.  Accordingly, the insertion loss is reduced. Therefore, the reflection return light is reduced while reducing the insertion loss.  
     [0063]FIG. 7 shows an optical module  40 C according to a fourth embodiment. The optical module  40 C has the same structure as the optical module  40 B shown in FIG. 6 except that the optical fiber array  42  and the lens array  44  are secured on an inclined surface  60   a  of a wedge spacer  60  such that the outgoing light A from the lens outgoing end surface, which is the right end surface  46   a  of the lens substrate  46 , is horizontal as viewed in FIG. 7. The wedge spacer  60  corresponds to an angle compensating member, which retains the optical fiber array  42  and the lens array  44  to be inclined with respect to a horizontal surface or a reference surface, such as a surface plate. To check whether the outgoing light A is horizontal, the above mentioned infrared sensor is used to measure the outgoing light A at two points at the same height.  
     [0064] The fourth embodiment provides the following advantages.  
     [0065] (m) Since the outgoing light A from the right end surface  46   a  of the lens substrate  46  is horizontal, the reflection return light is reduced.  
     [0066] It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.  
     [0067] In the above embodiments, the optical module includes the optical fiber array  42 , which has the optical fibers  41 , and the lens array  44 , which has the microlenses  43 . However, the present invention is not limited to have such structure, but may widely be applied to a collimator or a collimator array that includes an optical fiber array, which has at least one optical fiber, and a lens array, which has at least one microlens. For example, the present invention may be applied to a collimator (single collimator) that includes a single core capillary, which has an optical fiber, and a microlens.  
     [0068] In the above embodiments, the lens array  44  is formed by the flat microlens array in which the microlenses  43  are arranged in a line. However, the present invention may be applied to the lens array  44 , which is formed by the flat microlens array, in which the microlenses  43  are arranged in two dimensions.  
     [0069] In the above embodiments, the lens array  44  is formed by the flat microlens array on which microlenses, which are microlenses, are located. However, the present invention may be applied to a lens array that has at least one microlens, which is a gradient index rod lens.  
     [0070] In the above embodiments, the numerical value of each part is an example and can be changed as required.  
     [0071] In the first embodiment, the lens array  44  is constituted by the flat microlens array in which the microlenses  43  are formed on the lens substrate  46  by an ion-exchange method. However, the present invention is not limited to have such structure, but several types of microlenses may be used. For example, after forming a lenticular resin layer on a glass, a lens array may be manufactured by reactive ion etching (RIE) method using anisotropic etching, or a resin lens array may be manufactured by molding. The lens array  44  may be formed by arranging microlenses, which are gradient index rod lenses.  
     [0072] In the fourth embodiment, the wedge space  60  is used. However, the present invention need not use the wedge spacer  60 , but may use any member that can retain the optical fiber array  42  and the lens array  44  in an inclined state with respect to a horizontal surface, or a reference surface, such as a surface plate.  
     [0073] The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.