Patent Publication Number: US-2018031790-A1

Title: Optical couping module and optical communication apparatus using the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The instant disclosure relates to an optical coupling structure and an optical communication apparatus using the same; in particular, to an optical coupling structure and an optical communication apparatus capable of providing feedback of optical signals. 
     2. Description of Related Art 
     A conventional optical communication apparatus usually includes a light output device for outputting optical signal, an optical fiber for receiving and transmitting the optical signal, and an optical assembly for transmitting the optical signal to the optical fiber. To be more specific, the light output device, such as a laser, outputs the optical signal to the optical assembly so that the optical signal can be transmitted to the optical fiber through the optical assembly. 
     In addition, in order to maintain the output power stability and detect the deterioration of the light output device during normal lifetime under the operation conditions of normal operation temperature, the light output power of the light output device has to be monitored. Accordingly, the optical assembly needs to be improved in structure so that a portion of the optical signal can be guided to a monitor photodiode (MPD) for monitoring the light output power. 
     SUMMARY OF THE INVENTION 
     In order to achieve the aforementioned objects, an optical coupling structure and an optical communication apparatus using the same are provided in the instant embodiment. The coupling structure includes a light splitting portion disposed on an optical axis of the lighting element to guide the optical signal outputted by the lighting element respectively to an optical transmission unit and a photodetector. 
     An optical coupling structure provided in one of the embodiments of the instant disclosure includes a light incident portion, a light splitting portion, a first light emitting portion, and a second light emitting portion. The light incident portion is arranged for receiving an initial optical signal emitted by a lighting element, and the initial optical signal is converted into a parallel beam by passing through the light incident portion. The light splitting portion is disposed on an optical path of the parallel beam. The light splitting portion includes a first reflective surface, a second reflective surface, and a connecting surface connected between the first reflective surface and the second reflective surface so that a height difference exists between the first reflective surface and the second reflective surface. The parallel beam is divided into a first beam and a second beam through the first reflective surface and the second reflective surface, and the slopes of the first reflective surface and the second reflective surface are both positive or both negative. The first light emitting portion is disposed on an optical path of the first beam, in which the first beam is converted into a first optical signal through the first light emitting portion for transmitting to an optical transmission unit. The second light emitting portion is disposed on an optical path of the second beam, in which the second beam is converted into a second optical signal through the second light emitting portion for transmitting to a photodetector. 
     An optical communication apparatus is provided in the embodiment of the instant disclosure. The optical communication apparatus includes a lighting element for emitting an initial light signal, an optical transmission unit, a photodetector, and an optical coupling structure. The photodetector and the optical transmission unit are arranged at the same side of the lighting element. The optical coupling structure includes a light incident portion for receiving the initial optical signal, a light splitting portion, a first light emitting portion, and a second light emitting portion. The initial optical signal is converted into a parallel beam by passing through the light incident portion. The light splitting portion is disposed on an optical path of the parallel beam. The light splitting portion includes a first reflective surface, a second reflective surface, and a connecting surface connected between the first reflective surface and the second reflective surface so that a height difference exists between the first reflective surface and the second reflective surface. The parallel beam is reflected by the first reflective surface and the second reflective surface and divided into a first beam and a second beam, and slopes of the first reflective surface and the second reflective surface are both positive or both negative. The first light emitting portion is disposed on an optical path of the first beam, in which the first beam is converted into a first optical signal through the first light emitting portion for transmitting to an optical transmission unit. The second light emitting portion is disposed on an optical path of the second beam, in which the second beam is converted into a second optical signal for transmitting to a photodetector through the second light emitting portion. 
     To sum up, in the instant disclosure, the initial optical signal outputted by the lighting element enters the optical coupling structure, projects on two different reflective surfaces of the light splitting portion, and then is divided into a first beam and a second beam with different emission directions. The first beam and the second beam are respectively transmitted to the optical transmission unit and the photodetector. 
     Accordingly, the photodetector can receive the optical signal through the optical coupling structure to monitor the light output power of the lighting element. Once the deterioration of the lighting element or other problems occur, the lighting element can be repaired or replaced to maintain the stability of the optical communication. 
     In order to further the understanding regarding the instant disclosure, the following embodiments are provided along with illustrations to facilitate the disclosure of the instant disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view of a localized optical communication apparatus according to an embodiment of the instant disclosure; 
         FIG. 1A  shows an enlarged view of the region A shown in  FIG. 1 ; and 
         FIG. 2  shows a cross-sectional view of a localized optical coupling structure according to another embodiment of the instant disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a cross-sectional view of a localized optical communication apparatus according to an embodiment of the instant disclosure. The optical communication apparatus  1  includes a lighting element  11 , a photodetector  12 , an optical transmission unit  13 , and an optical coupling structure  14 . In the instant disclosure, an initial optical signal L outputted by the lighting element  11  can be converted into a first optical signal L 1  and a second optical signal L 2  through the optical coupling structure  14 , and the first optical signal L 1  and the second optical signal L 2  are respectively transmitted to the optical transmission unit  13  and to the photodetector  12 . The details are described as follows. 
     The lighting element  11  converts an electrical signal into the corresponding initial optical signal L and then transmits the initial optical signal L to the optical coupling structure  14 . The lighting element  11  can be a laser or other light source. In the instant embodiment, the lighting element  11  is a vertical cavity surface emitting laser (VCSEL). In addition, the initial optical signal L outputted by the lighting element  11  can have a wavelength ranging from 850 nm to 980 nm. 
     The optical transmission unit  13  is positioned at one side of the optical coupling structure  14  to receive the first optical signal L 1 , which is transmitted by the optical coupling structure  14 . Thereafter, the first optical signal L 1  can be transmitted to a photo receiver (not shown in  FIG. 1 ) through the optical transmission unit  13 . In the embodiment of the instant disclosure, the optical transmission unit  13  can be an optical fiber. 
     The photodetector  12  positioned at another side of the optical coupling structure  14  receives the second optical signal L 2  transmitted by the optical coupling structure  14  to detect the intensity and stability of the initial optical signal L. In one embodiment, the photodetector  12  can be a photodiode, and the lighting element  11  and the photodetector  12  are mounted on the same circuit board (not shown). The photodetector  12  can convert the received second optical signal L 2  into a current signal and then provide a feedback to a control unit (not shown), which is electrically connected to the lighting element  11 . The control unit monitors and adjusts the light output power of the lighting element  11  according to the current signal transmitted by the photodetector  12 . In the instant embodiment, the optical transmission unit  13  and the photodetector  12  are located at the same side of the lighting element  11 . 
     In the embodiment of the instant disclosure, the optical coupling structure  14  includes a light incident portion  141 , a light splitting portion  142 , a first light emitting portion  143 , and a second light emitting portion  144 . 
     Please refer to  FIG. 1A , which shows an enlarged view of the region A of the optical communication apparatus shown in  FIG. 1 . In the instant embodiment, the light incident portion  141  is located at a position corresponding to the position of the lighting element  11  to receive and convert the initial optical signal L to a parallel beam L′. The light incident portion  141  of the optical coupling structure  14  includes a collimating lens  141   a  for converting the initial optical signal L into the parallel beam L′. The collimating lens  141   a  can be a micro-lens unit for converting a divergent beam into a parallel beam. 
     The light splitting portion  142  disposed on an optical path of the parallel beam L′ includes a first reflective surface  142   a  and a second reflective surface  142   b  for dividing the parallel beam L′ into a first beam L 1 ′ and a second beam L 2 ′ with different emission directions. To be more specific, the parallel beam L′ projects on an interface between the first reflective surface  142   a  and the second reflective surface  142   b . One portion of the parallel beam L′ reflected by the first reflective surface  142   a  forms the first beam L 1 ′, which finally emits out of the optical coupling structure  14  through the first light emitting portion  143 . The other portion of the parallel beam L′ reflected by the second reflective surface  142   b  forms the second beam L 2 ′, which finally emits out of the optical coupling structure  14  through the second light emitting portion  144 . 
     An extending direction of the first reflective surface  142   a  and an optical axis of the collimating lens  141   a  form a first acute angle θ1, and an extending direction of the second reflective surface  142   b  and the optical axis of the collimating lens  141   a  form a second acute angle θ2. The first acute angle θ1 can be equal to or less than the second acute angle θ2. 
     The first light emitting portion  143  receives the first beam L 1 ′ reflected by the first reflective surface  142   a , and converts the first beam L 1 ′ into the first optical signal L 1  for inputting to the optical transmission unit  13 . The second light emitting portion  144  receives the second beam L 2 ′ reflected by the second reflective surface  142   b , and converts the second beam L 2 ′ into the second optical signal L 2  for inputting to the photodetector  12 . 
     The positions of the first and second light emitting portions  143 ,  144  respectively correspond to the position of the optical transmission unit  13  and the position of the photodetector  12 . In the embodiment of the instant disclosure, since the lighting element  11  and the photodetector  12  are disposed on the same circuit board, the light incident portion  141  and the second light emitting portion  144  are located at the same side of the optical coupling structure  14 . Furthermore, the first light emitting portion  143  and the light incident portion  141  are respectively located at two adjacent sides of the optical coupling structure  14 . 
     In the instant embodiment, the first light emitting portion  143  includes a first optical lens  143   a  for receiving the first beam L 1 ′, and the second light emitting portion  144  includes a second optical lens  144   a  for receiving the second beam L 2 ′. The first and second optical lenses  143   a ,  144   a  can be convex lenses or Fresnel lenses. The first optical lens  143   a  receives and converges the first beam L 1 ′ to output the first optical signal L 1 . The second optical lens  144   a  receives and converges the second beam L 2 ′ to output the second optical signal L 2 . In other words, the first beam L 1 ′ can be converged to form the first optical signal L 1  by the first optical lens  143   a , and the second beam L 2 ′ can be converged by the second optical lens  144   a  to form the second optical signal L 2 . 
     In the embodiment of the instant disclosure, the numbers of the collimating lens  141   a , the first optical lens  143   a , and the second optical lens  144   a  can be one or more, which depends on the number of the lighting elements  11 , the optical transmission units  13 , and the photodetectors  12 . 
     Please refer to  FIG. 1A . The light splitting portion  142  further includes a connecting surface  142   c  connected between the first reflective surface  142   a  and the second reflective surface  142   b  so that a height difference exists between the first and second reflective surfaces  142   a ,  142   b . That is, the light splitting portion  142  includes a step difference structure. 
     Specifically, an extending direction of the connecting surface  142   c  is substantially parallel to the optical axis of the collimating lens  141   a . The parallel beam L′ projects on the light splitting portion  142  in a direction parallel to the connecting surface  142   c  so as to be divided into the first beam L 1 ′ and the second beam L 2 ′. In the instant embodiment, the first acute angle θ1 can be equal to the second acute angle θ2. That is, the first reflective surface  142   a  is parallel to the second reflective surface  142   b.    
     Moreover, the slopes of the first and second reflective surfaces  142   a ,  142   b  can be both positive or both negative. In the embodiment of the instant disclosure, since the optical transmission unit  13  and the photodetector  12  are both positioned at the right-side of the lighting element  11 , the slopes of the first and second reflective surfaces  142   a ,  142   b  are both positive. 
     Please refer to  FIG. 1  and  FIG. 1A . In the instant embodiment, the optical coupling structure  14  includes a recess portion  140  located at the side opposite to the side at which the light incident portion  141  is located. The first reflective surface  142   a , the second reflective surface  142   b  and the connecting surface  142   c  are disposed on an inner wall of the recess portion  140 . That is, the first reflective surface  142   a , the second reflective surface  142   b  and the connecting surface  142   c  are parts of the interface between two different media (i.e., the optical coupling structure  14  and air). In one embodiment, the first reflective surface  142   a  and the second reflective surface  142   b  can be coated with a totally reflective film or a partially reflective film, which is not limited in the instant disclosure. The first acute angle θ1 and the second acute angle θ2 can be total reflection angles of the optical coupling structure  14  or not, designed according to the material of the optical coupling structure  14  or the materials of the reflective films coated on the first reflective surface  142   a  or the second reflective surface  142   b.    
     Upon the condition that both the first acute angle θ1 and the second acute angle θ2 are total reflection angles, the refraction of the parallel beam L′ projecting on the first and second reflective surfaces  142   a ,  142   b  from the optical coupling structure  14  to air would not occur. On the contrary, upon the condition that neither the first acute angle θ1 nor the second acute angles θ2 is a total reflection angle, a portion of the parallel beam L′ projecting on the first and second reflective surfaces  142   a ,  142   b  may be refracted to air. 
     Please refer to  FIG. 1A . Furthermore, the optical coupling structure  14  further includes an inclined reflective surface  145 . The inclined reflective surface  145  and the light splitting portion  142  are formed on the inner wall of the recess portion  140 . The inclined reflective surface  145  is arranged at a position corresponding to the position of the second light emitting portion  144 . The inclined reflective surface  145  is arranged on an optical path of the second beam L 2 ′, facing to the second reflective surface  142   b  so that the second beam L 2 ′ can be guided by the inclined reflective surface  145  to the second optical lens  144   a.    
     The second reflective surface  142   b  and the inclined reflective surface  145  incline toward each other. That is, if the second reflective surface  142   b  has a positive slope, the inclined reflective surface  145  has negative slope. On the contrary, if the second reflective surface  142   b  has a negative slope, the inclined reflective surface  145  has a positive slope. The inclined reflective surface  145  is spaced apart from an optical path of the first beam L 1 ′. Accordingly, the lowest end of the inclined reflective surface  145  is located at a higher level than the highest end of the first reflective surface  142   a . Preferably, a horizontal extending plane where the lowest end of the inclined reflective surface  145  is located intersects the connecting surface  142   c  to ensure that the inclined reflective surface  145  can reflect the second beam L 2 ′ and will not block the first beam L 1 ′. 
     In one embodiment, the inclined reflective surface  145  and the light splitting portion  142  are commonly formed at the bottom of the recess portion  140 , and the inclined reflective surface  145  is a total reflection surface. In another embodiment, a mirror coating or a light reflective sheet can be disposed on the first reflective surface  142   a , the second reflective surface  142   b  and the inclined reflective surface  145 . As long as the first beam L 1 ′ and the second beam L 2 ′ can be respectively guided to the first light emitting portion  143  and the second light emitting portion  144 , the reflective materials for forming the first reflective surface  142   a , the second reflective surface  142   b  and the inclined reflective surface  145  are not limited in the instant disclosure. 
     In the optical communication apparatus  1  of the instant embodiment, the lighting element  11  emits the initial optical signal L to the optical coupling structure  14 , and the initial optical signal L is converted into the parallel beam L′ through the collimating lens  141   a . The parallel beam L′ is in alignment with an extending direction of the connecting surface  142   c  and projects on the first and second reflective surfaces  142   a ,  142   b . Thereafter, the parallel beam L′ is divided into the first beam L 1 ′ and the second beam L 2 ′. The first beam L 1 ′ is converged by the first optical lens  143   a  of the first light emitting portion  143  to form the first optical signal L 1  for transmitting to the optical transmission unit  13 . Additionally, the second beam L 2 ′ is reflected by the inclined reflective surface  145  to project the second light emitting portion  144 , and then the second beam L 2 ′ is converged by the second optical lens  144   a  to form the second optical signal L 2  for transmitting to the photodetector  12 . Accordingly, the photodetector  12  converts the second optical signal L 2  into the current signal and provides a feedback to the control unit so that the control unit can monitor and adjust the light output power of the lighting element  11  according to the feedback (the received current signal). As such, by receiving the second optical signal L 2 , the photodetector  12  can detect the intensity and stability of the initial optical signal L. 
     Please refer to  FIG. 2 , which shows a cross-sectional view of an optical coupling structure according to another embodiment of the instant disclosure. The same reference numerals are given to the same components or to components corresponding to those in  FIG. 1A , and descriptions of the common portions are omitted. 
     The optical coupling structure  14 ′ of the instant disclosure does not include the inclined reflective surface  145  as shown in  FIG. 1A . In addition, the first reflective surface  142   a  and the second reflective surface  142   b  have different slopes. That is, the second acute angle θ2 formed between the second reflective surface  142   b  and the optical axis of the collimating lens  141   a  is larger than the first acute angle θ1 formed between the first reflective surface  142   a  and the optical axis of the collimating lens  141   a.    
     In the instant embodiment, the second beam L 2 ′ reflected by the second reflective surface  142   b  directly projects on the second outputting portion  144  without passing through the inclined reflective surface  145 . Accordingly, the optical axis of the second optical lens  144   a  of the second outputting portion  144  is arranged to be inclined with respect to the optical axis of the collimating lens  141   a  at an angle so that the second beam L 2 ′ can be converged by the second optical lens  144   a  and focus on the photodetector  12 . 
     To sum up, in the optical coupling structures and the optical communication apparatus provided in the embodiments of the instant disclosure, the light output power of the lighting element can be monitored by the photodetector. In the instant disclosure, the light splitting portion of the optical coupling structure includes two reflective surfaces having the same or different slopes, and a height difference is formed between these two reflective surfaces. The initial optical signal L outputted by the lighting element enters the optical coupling structure, projects on two different reflective surfaces of the light splitting portion to be divided into the first beam and the second beam respectively emitting toward different directions. The first beam and the second beam are respectively transmitted to the optical transmission unit and the photodetector. 
     As such, the light output power of the lighting element can be monitored according to the second optical signal. Once the deterioration of the lighting element or any other problems occur, the lighting element can be repaired or replaced to maintain the stability of the optical communication. In addition, the parallel beam can be divided by the light splitting portion of optical coupling structure in the instant disclosure, and an additional splitter can be omitted to reduce cost. 
     The descriptions illustrated supra set forth simply the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.