Abstract:
The present invention relates to a module for parallel transmission and reception of an optical signals, and particularly a miniaturized module with a fixed optical coupler and a detachable electric connector is disclosed. A miniaturized optical signal transmission module according to the present invention comprises an electrical connector for coupling electric signals to a circuit board; an array of optical devices coupled to metal leads, the array of optical devices converting between optical signals and the electric signals; an optical fiber array block fixedly and optically coupled to the array of optical devices for transmitting the optical signals, wherein the metal leads are detachably coupled to the electrical connector part. The optical module can be miniaturized so that the entire system can be miniaturized. Accordingly, many advantages according to the miniaturization of the entire system can be obtained.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of application Ser. No. 09/690,172, filed Oct. 16, 2000 abandoned. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a module for transmitting and receiving optical signals through optic fibers, and, more particularly, to a coupling module having a detachable electrical connector for coupling electrical signals to the module. 
     2. Description of the Prior Art 
     Increasingly, the technical progress of computer systems requires massive data transmission at high transmission rates to computer peripherals such as monitors, hard discs, printers, and the like. Additionally, the development of the internet accelerates the need for high-speed connections between computer systems so as to lead to a trend of high speed data transmission between separate computer systems. 
     In responding to this trend, data transmission with existing electrical wires reveals limitations in electrical cabling, including the bandwidth limitations of electrical wires and the effects of electromagnetic wave interference in transmission signals characteristic of high data transmission rates. Accordingly, in order to overcome the limitations of such electric signal transmission, the data transmission field is increasingly looking towards optical signal transmission methods using optical fiber for high rate data transmission. 
     Optical transmission of data at high transmission rates has several advantages. For example, optical fibers provide higher bandwidth data transmission at lower error rates without the electromagnetic interference inherent in adjacent electrical transmission lines, overcoming two of the primary problems of data transmission over electrical cabling. Complementary optical signal transceiver modules, then, easily cope with the parallel data transmissions that are desirable in many computer system applications. 
     Conventional parallel optical signal transceiver modules have detachable optical connectors with fixed electrical connections to an external electric circuit. However, the detachable optical connector must have a structure allowing connections and separations. Due to alignment problems inherent in manufacture and in aging of the connector, these connections can become unstable so that the coupling of optical data into or out of the optical fibers is degraded. Such unstable connections may cause the loss or the transformation of transmission data, which is a serious drawback to an optical connector requiring a high reliability of optical data transmission. In addition, the connection part of the detachable optical connector can become polluted with pollutants such as dust and other contaminates, which may also degrade the transmission of optical signals. 
     One approach to the alignment problem is to more rigidly support the connector part to provide better alignment to the optical fibers. However, this approach increases the size of the connector. As the size of the optical connection part gets larger, the entire system which utilizes the optical connector gets larger as well. The larger size of a system deteriorates space utility efficiency, leading to a reversal in the miniaturization trend, and therefore is an undesirable result. For example, the miniaturization of electrical circuit components built in an electric circuit board lowers the height of the built-in electric circuit components to about 1˜2 mm levels from the surface of the electric circuit board, but the height of the conventional optical parallel transceiver module becomes about 1 cm, leading to a difficulty in miniaturizing systems requiring optical connections. 
     Therefore, there is a need for optical transceiver modules having small form factors that do not suffer the degradation of optical transmission due to alignment or contamination. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an optical transceiver system having a detachable electrical connection is presented. Because an electrical connection is detached, rather than the optical connection as is conventional, an optical transceiver system in accordance with the present invention does not suffer from contamination of the optical components or from degradation of the optical alignment due to repeated attaching and detaching operations. Additionally, embodiments of an optical transceiver system in accordance with the present invention can have small form factors in conformity with the about 1 to about 2 mm height of the external circuitry to which the transceiver system is coupled. 
     In some embodiments, a miniaturized optical transceiver module according to the present invention comprises an electrical connector for coupling an electric signal between an external circuit board and the miniaturized optical transceiver module; an optical device array detachably coupled to the electrical connector so that electrical signals are transmitted between the electrical connector and optical devices in the optical device array; and an optical fiber array block fixedly mounted in the optical device array block so that optical fibers of the optical fiber array are optically coupled to the optical devices of the optical device array. In some embodiments, the electrical connector is fixed on the external circuit board. In some embodiments, an optical device array includes any number of light emitters and optical detectors. In some embodiments, the optical device array includes either light emitters or optical detectors. 
     These and other embodiments are further described below with respect to the following figures. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a block diagram of a complementary pair of parallel optical transceiver modules according to an embodiment of the present invention. 
     FIG. 2 is an exploding view of an embodiment of an optical transceiver module according to an embodiment of the present invention. 
     FIG. 3 shows an assembled view of the embodiment of the transceiver module shown in FIG.  2 . 
     FIG. 4 shows a cross-sectional view of the embodiment of the transceiver module shown in FIG.  2 . 
     FIG. 5 is an exploding view of another embodiment of an optical transceiver module according to the present invention. 
     FIG. 6 shows an assembled view of the embodiment of the optical transceiver shown in FIG.  5 . 
     FIG. 7 is a cross-sectional view of the optical signal transmission/receiver part of FIG.  5 . 
     FIG. 8 is a block diagram of another embodiment of an optical transceiver module according to the present invention. 
    
    
     In the figures, elements having the same designation between figures have the same function. 
     DETAILED DESCRIPTION 
     FIG. 1 shows a block diagram of a parallel optical transceiver system  140  according to an embodiment of the present invention. System  140  includes optical module  100  and optical transceiver module  200 , which are coupled by optical fibers  136 . Optical module  100  in FIG. 1 includes electrical connector  110 , optical device array  120 , and optical fiber coupler  130 . Optical module  200  includes electrical connector  210 , optical device array  220 , and optical fiber coupler  230 . In some embodiments, optical device array  120  includes an array of light emitters and optical device array  220  includes a corresponding array of optical detectors. In general, optical device array  120  can include any number of individual optical detectors and light emitters. Optical device array  120  is complementary to optical device array  220  in that optical signals transmitted by a light emitter of optical device array  120  is received, through one of optical fibers  136 , by a corresponding light detector of optical device array  220 . Conversely, an optical signal transmitted by a light emitter of optical device array  220  is received, through one of optical fibers  136 , by a corresponding light detector of optical device array  120 . The light emitters of optical device array  120  are optically coupled with the optical detectors of optical device array  220  through optical fibers  136 . Electrical signals are coupled to the light emitters of optical device array  120  through electrical connector  110 . Optical signals are coupled into optical fibers  136  through optical fiber array block  130 . Additionally, optical signals are coupled into the optical detectors of optical device array  220  through optical fiber array block  230  and electrical signals are coupled out of optical device array  220  through electrical connector  210 . 
     Optical device arrays  120  and  220  are arranged with optical fiber arrays  130  and  230 , respectively, so that optical signals are coupled between the optical devices of optical device arrays  120  and  220  and the optical fibers of optical fiber arrays  130  and  230 . In some embodiments, the optical fibers coupled between optical fiber arrays  130  and  230  each have a mirror face processed to be, for example, 45 degree slanted and positioned proximate an upper side of the devices of optical device arrays  120  and  220  in order to couple optical signals between the devices of optical device arrays  120  and  220 , respectively, and the optical fibers of optical fiber array blocks  130  and  230 , respectively. 
     Described in detail, in embodiments with a 45 degree slanted mirror face the optical signals are reflected from the 45 degree slanted mirror face placed on the upper side of the light emitting device array and transmitted to optical fibers  136 . The optical signals transmitted through the optical fiber array  136  is reflected from a mirror face processed to be 45 degree slanted so as to be transmitted to an arranged light receiving device, thereby achieving the transmission and reception of the optical signals. One advantage of utilizing a 45 degree slant processed optical fiber in optical fiber array blocks  130  and  230  is that wire bonding for connecting optical devices and electrical connections in electrical connectors  110  and  210  are facilitated. Additionally, the arrangement of optical fibers and optical devices is facilitated. 
     Alternatively, in some embodiments of the invention light is coupled between the optical devices of optical device arrays  120  and  220  and the optical fibers of optical fiber array blocks  130  and  230 , respectively, directly. The optical device is arranged adjacent to an optical fiber array on the same layer. Advantageously, the slant-processed faces of optical fiber array blocks  130  and  230  are not necessary, thereby removing one processing step. However, despite that advantage, this structure can be problematic because the efficiency of optical coupling with optical fiber  136  is deteriorated due to the difficulties of coupling signals from optical devices in optical device arrays  120  and  220  to optical fiber  136 . 
     FIG. 2 shows an exploded view of one embodiment of an optical transceiver module  300 , which can be either of optical module  100  or optical module  200  (FIG.  1 ). Optical module  300  includes an optical device array block  145  having an array of optical devices  124 , an optical fiber array block  134  having an array of optical fibers  136 , and an electrical connector  161 . Optical fiber array block  134  is fixedly inserted into optical device array block  145  so that light is coupled between optical devices  124  and optical fibers  136 . A cover  150  is attached to optical device array block  145  in order to hold optical fiber array block  134  rigidly in place. Optical fiber array block  145  also includes electrical leads  202  on structural  146  coupled to optical devices  124  so that electrical signals can be transmitted to optical devices  124 . Electrical leads  202  are electrically coupled with corresponding leads  164  in electrical connector  161  by slidably attaching optical device array block  145  into electrical connector  161 . In some embodiments, small gaps  210  in structure  146  on either side of electrical leads  202  assist in aligning and attaching optical device array block  145  with electrical connector  161 . Module  300 , therefore, is detachable between electrical connector  161  and optical device array block  145 . 
     Optical devices  124  may be either light emitting devices, optical detectors, or a mixture of light emitting devices and optical detectors. A light emitting device can be any device for converting an electrical signal into an optical signal, such as an edge-emitting laser diode, vertical cavity surface emitting laser diode(VCSEL), light emitting diode(LED), or the like. A VCSEL, in particular, is advantageously utilized as one of optical devices  124  because a VCSEL has a lower electric power consumption due to a low threshold current necessary for a laser oscillation, and a VCSEL emits a circular beam pattern identical to a mode pattern of an optical fiber, and is easily optically coupled to an optical fiber since the radiation angle indicating the extent of divergence according to laser beam propagation is small. Furthermore, a VCSEL is easily characterized; the characteristics of a VCSEL can be directly measured on a manufactured wafer since the VCSEL emits light from the wafer surface. An edge-emitting laser diode, for example, must be cleaved into individual devices after manufacture before the characteristics of light emitted from the chip edge can be tested. Therefore, the VCSEL is a light emitting device that facilitates a lowered cost of mass production. A VCSEL of this type is manufactured by Honeywell or Truelight. 
     Optical detectors which can be utilized as optical detector devices in optical device array  124  include any device for converting an optical signal into an electrical signal. Optical detectors can be produced from semiconductor materials such as Si, GaAs, and InP, for example. In particular, optical detectors for utilization as optical device  124  can be avalanche photodiodes, pin photodiodes, MSM photodiodes, or other similar devices. A common photodiode is manufactured by Truelight. 
     In general, the operating speed of an optical detector, such as a photodiode, is dependent on the light-receiving area of the optical detector. As the light-receiving area of a photodiode gets larger, the diode capacitance gets larger and the response time with respect to a changing optical intensity becomes slower. It, then, is necessary to reduce the light-receiving area of a light-receiving device in order for data signals to be transmitted at high data transmission rates. However, as the light-receiving area gets smaller, the amount of light coupled into the optical detector from an optical fiber is reduced. Therefore, the appropriate light-receiving area is determined by balancing the need to couple light into the optical detector with the need for a fast response time. 
     Optical fibers  136  can be any optical transmission medium. Generally, media employed for optical transmission include single-mode silica fiber, multi-mode silica fiber, and plastic optical fiber. In general, single-mode silica optical fiber has a core diameter of a few micrometers to about 10 μm through which light is propagated, a clad diameter of about 125 μm, and an overall diameter of about 250 μm with a polymer material coated on the outer periphery. Alignment of the single-mode silica optical fiber is critical since the diameter of the core is so small. However, the modal dispersion of a single-mode silica optical fiber is small since the single-mode fiber supports only one optical mode and therefore the single-mode fiber is suitable for long distance transmission, for example up to about a few kilometers. 
     Two kinds of multi-mode silica optical fibers are widely used and their core diameters are about 50 μm and about 62.5 μm, respectively. The clad diameter is about 125 μm as in the single mode optical fiber and a polymer material is utilized for overall coating so that the entire diameter is about 250 μm. The multi-mode optical fiber, with its larger diameter core, facilitates optical coupling into the fiber. Therefore, the alignment of a multi-mode fiber is not as critical. However, due to a larger modal dispersion, the transmission distance is typically limited to about a few hundred meters. 
     Plastic optical fiber using plastic materials such as poly-methyl-methacrylate(PMMA) and the like instead of silica glass can also form optical fibers for optical fiber  136 . Plastic fibers can be manufactured with diverse core diameters of from a few tens of micrometers to about 1 mm because of the flexibility of the materials. As the core diameter gets larger less alignment precision is required, which has the advantage of making optical components requiring alignment easier. However, since the number of propagation modes is increased, the transmission distance may be restrained due to the larger light dispersion by a light propagation speed difference between the modes. For example, if the core diameter of a plastic optical fiber is 240 μm, the transmission distance may be limited due to dispersion to a few tens of meters at a data transmission rate of several hundred Mbps. 
     In the embodiment shown in FIG. 2, optical fibers  136  are fixedly attached in optical fiber array block  134 . Optical fiber array block  134  can be formed with tip ends of optical fibers  136  fixedly arranged with specified intervals within a molded plastic restraint  200 . In some embodiments, the tip ends of optical fibers  136  along with molded plastic restraint  200  is polished with, for example, a 45 degree slant-polished mirror face  132  for coupling light between optical device array  124  and optical fibers  136 . Optical fiber array block  134  may be manufactured with molded restraint  200  being a transparent material by molding the transparent material, after individual fibers of optical fibers  136  are arranged with specified intervals and heights, over optical fibers  136  and polishing face  132 . In some embodiments, optical fibers  136  can be adhered to glass with an optical adhesive and face  132  can be formed directly on the tips of optical fibers  136 . In some embodiments, optical fibers  136  can be placed in V-shaped grooves, respectively, formed in an array in certain intervals on a substrate. 
     In order to obtain large optical coupling between optical fibers  136  and device array  124 , optical fibers  136  are formed close to the bottom of optical fiber array block  134 . The separation between device array  124  and face  132 , therefore, should be as small as possible. Further, a thin-film of evaporated aluminum on face  136  helps form a mirror face to further couple light between optical fibers  136  and optical device array  124 . 
     Optical fiber array block  134  is inserted into slot  204  in module base  145 . Slot  204  is arranged to receive optical fiber array  134  and hold optical fiber array  134  rigid so that optical fibers  136  are positioned directly above device array  124 . Light from device array  124 , then, is reflected into optical fibers  136  by face  132 . Conversely, light from optical fibers  136  are reflected into device array  124  by face  132 . One skilled in the art will recognize that face  132  can be polished at any angle such that light from optical fibers  136  is reflected onto optical device array  124  and light emitted by optical device array  124  is reflected into optical fibers  136 . 
     Optical device array block  145 , in one embodiment, includes a structure  146  on which metal leads  202  are supported. Structure  146  can be a metal lead frame or a flexible printed circuit board. In some embodiments, a metal plate  143  is included on which optical devices  124  are mounted. Metal leads  202  are electrically coupled to optical devices  124  so that electrical signals are coupled between optical devices  124  and metal leads  202 . 
     Optical device array block  145  can be manufactured by injection molding around structure  146 . Structure  146  can be, for example, a metal lead frame or a flexible printed circuit board. In some embodiments, structure  146  includes a metal plate  143  on which optical device array  124  is mounted. Driving current or bias voltages can be supplied to light emitters or photodiodes of optical device array  124  through metal leads  202  on structure  146 . Additionally, electrical contact with the back side of optical devices in optical device array  124  can be accomplished through metal plate  143 . In some embodiments, gold line wiring  122  provides electrical connections between the optical devices of optical device array  124  and individual ones of metal leads  202 . Slot  204  in optical device array  145  receives optical fiber array block  134  such that optical fibers  136  are aligned with optical device array  124 . 
     In some embodiments, light from light emitters in device array  124  passes through the bottom side of optical fibers  136  on which, for example, a 45 degree slanted mirror face  132  is formed. The light is then reflected from mirror face  132  and propagates through optical fibers  136 . Additionally, light propagated through optical fibers  136  is reflected from mirror face  132  at the tip ends of optical fibers  136 , passes through the bottom side of optical fibers  136 , and is incident on a light-receiving face of a photo detector of optical device array  124 . The height of optical fiber array block  134  is larger than the diameter of individual fibers of optical fibers  136 , but can be manufactured to be about 0.5 to about 1 mm for miniaturization of the entire optical transceiver module  300 . 
     Grooves  141  and  142  are provided on both sides of optical device array block  145  to accommodate a metal cover  150 . Metal cover  150  includes matching protrusions  206  and  152 , respectively, so that metal cover  150  can be attachably fixed to optical device array block  145  after optical fiber block  134  is inserted into groove  204 . In some embodiments, handles  144  can be provided on the sides of optical device array block  145  to facilitate attaching and detaching electrical connectors  161  with optical device module  145 . In some embodiments, the resulting height of module base  145  is manufactured to be about 1 to about 2 mm for miniaturization. 
     Metal cover  150  can be manufactured by folding a metal plate, which in some embodiments has a thickness of about 200 μm. Metal cover  150  is inserted into module base  145  so that protrusions  206  slide into grooves  141 . Latch plates  152  formed on cover  150  is latched into grooves  142  formed on both sides of the module base  145  in order to securely fix cover  150  to module base  145 . 
     Metal cover  150  has multiple purposes, including protection of the interior of optical device module  145  from dust and other contaminants. Metal cover  150  can also provide a heat-sink function when thermally contacted by heat-radiating metal plates  143  on both sides of module base  145 . Metal cover  150  can also prevent malfunctions of the module of the present invention by electromagnetic shielding of optical devices in optical device module  145 . 
     Module  145  is further arranged to mate with electrical connector  161 . Electrical connector  161  includes a housing  208  that slidably attaches with insert  210  of module  145  so that metal leads  202  are electrically coupled to metal leads  164 . In some embodiments, a metal band  162  and solder portions  163  allow electrical connection part  161  to be mounted to a circuit board. In some connections, metal leads  164  may be coupled into an electrical cable. 
     FIG. 3 shows electric connector part  161  attached on a printed circuit board  165 . Metal leads  164  can be soldered on a wiring pattern  166  on printed circuit board  165 , and left and right soldering portions  163  of a metal holder  162  can be fixedly soldered on fixture patterns or contacts  167  on printed circuit board  165 . In some embodiments, connector part  161  can be epoxied or otherwise attached to circuit board  165 . FIG. 3 further shows the assembled combination of metal cover  150 , optical fiber block  134 , and device module  145 . 
     FIG. 4 is a cross-sectioned view of electric connector  161  engaged with optical module  145 . FIG. 4 shows one of metal leads  164  of electrical connector  161 . 
     Each metal lead of metal leads  164  has a spring portion  212  to contact with one of metal leads  202  from device module  145 . Structure  146  of module  145 , with one of metal leads  202 , is pressed under spring portion  212 , thereby making an electrical contact between metal leads  202  of device module  145  and metal leads  164  of electrical connector  161  and holding module  145  in place relative to electrical portion  161 . Metal leads  164  can be soldered to pattern  166  on circuit board  165 . Gold wire  122  makes electrical contact between one of optical device array  124  and one of metal leads  202 . In some embodiments, metal leads  202  are held in place by epoxy  126 . 
     Further, one of optical device array  124  is arranged relative to one of optical fibers  136  in optical fiber array block  134 . In some embodiments, optical fiber block  134  includes a 45 degree slanted mirror face  132 . The space between optical fibers  136  and optical device array  124  and an area of the gold line wiring  122  can be filled with a transparent optical adhesive  126  to be firmly engaged. Adhesive  126  in the area of gold line wiring  122  and the optical connection area between the one of optical fibers  136  and the corresponding one of optical device array  124  may protect these components from the external environment. 
     In some embodiments, optical adhesive  126  can have nearly the same refractive index as optical fibers  136 . By using the optical adhesive having nearly the same refractive index as the optical fiber, a reflection loss on the bottom side of optical fibers  136  may be reduced when compared to embodiments where the space between optical fibers  136  and optical device array  124  contains air having the refractive index of 1. 
     In some embodiments, portions of optical fibers  136  outwardly extended from device module  145  are molded with a stress buffering part  147 , which can be a flexible material such as silicone rubber and the like. Stress buffering part  147  is formed in order to prevent bending of optical fibers  136  in case an external force is exerted on optical fibers  136 . 
     FIG. 5 shows an exploded view of another embodiment of an optical module according to the present invention. Optical module  500 , which can be either of optical module  100  or optical module  200  (FIG.  1 ), differs from optical module  300  shown in FIG. 5 in the electrical connector. 
     Optical fiber block  134  of FIG. 5 includes optical fiber array  136  spaced and fixed in block  200 . Block  200  and optical fiber array  136  have polished surface  132 , which in some embodiments is a 45° angled and mirrored surface. Optical fiber block  134  is inserted into groove  204  of optical device module  145  so that optical fibers of optical fiber array  136  are fixedly positioned relative to individual optical devices of device array  124 . Device array  124  can be mounted on metal plate  143 . Electrical connections to metal leads  202  in optical device module  145  can be formed with gold wires  122 . Cover  150 , having ridges  206  and  152 , can be positioned with grooves  141  and  142  on module  145  to hold optical device module  134  in place and provide protection for optical device module  134 , as has been previously described. Metal cover  150  can be positioned around module  145  so that groove  171  is protruding. 
     In FIG. 5, optical device array  124  is electrically coupled to an elastomeric connector  148 . Elastomeric connector  148  has a structure formed with silicon rubber and a stacked conductor. If a conductor is pressed on both sides of elastomeric connector  148 , electrical contact is made between the conductors. Such elastomeric connectors are already commercialized and widely used for electrical connections to liquid crystal displays and the like, for example the elastomeric connector produced by Fujipoly Corp. 
     The stacked interval of the silicon rubber and the conductor in elastomeric connector  148  is formed with a pitch of around 100 μm, so that elastomeric connector  148  can be used in electrically connecting plural electrical contacts simultaneously. An upper side of the elastomeric connector  148  of FIG. 5 is electrically contacted with structure  146  having metal leads  202  coupled to device array  124 . The lower side of elastomeric connector  148  is slightly protruded from the bottom side of module base  145  so as to be contacted with the electrical contacts arranged on a printed circuit board  165 . 
     A module holder  180  can be manufactured by folding a metal plate of, for example, a 200 μm thickness. Module holder  180  can be soldered on a printed circuit board  165  in which the optical signal transmission module or the optical signal reception module is mounted in order for the transmission and reception modules to be easily detachable and to be arranged with contacts  166  on printed circuit board  165 . A latch groove  171  is provided on the upper and side surfaces of module base  145  of optical signal transmission module  500  so as to carry out a latch operation when engaged with the module holder  180 . 
     In some embodiments, a finger stop  181  can be press-manufactured in a convex shape in module holder  180  to operate with latch groove  171  and fix module  145  in place with module holder  180 . A module insertion part of the holder  180  secures an electrical contact through a close contact with elastomeric connector  148  by a spring action. 
     FIG. 6 shows module  145  assembled with cover  150  and optical fiber module  134  and module holder  180  mounted on circuit board  165  for receiving module  145 . Module holder  180  can be provided with soldering parts  182  on both sides to be fixed on printed circuit board  165 . Soldering parts  182  are positioned to align metal leads  166  with metal leads  202  of module  145  through elastomeric connector  148  when module  145  is coupled with module holder  180 . 
     FIG. 7 illustrates a cross sectional view of module  145  when engaged with module holder  180 . As has been discussed before, metal leads  202  is coupled to an optical device of optical device array  124  with gold wire  122 . The space between the optical device and the corresponding one of optical fibers  136  can be filled with transparent adhesive  124 . Metal leads  202 , supported by structure  146 , makes electrical contact with elastomeric connector  148 . Elastomeric connector  148  is held in place over metal lead  166  on circuit board  165  by module holder  180  so that an electrical coupling is created between one of metal leads  202  and the corresponding one of metal leads  166 . 
     FIG. 8 shows a modified arrangement of a parallel optical signal transceiver module  800  according to an embodiment of the present invention for a long distance transmission. Optical transceiver module  802  can be, for example, optical transceiver module  300  of FIG. 2 or optical transceiver module  500  of FIG. 5, or any other optical transceiver module according to the present invention. As described above, optical transceiver module  802  includes an optical device module  804  detachable from an electrical connector  806 . 
     Optical fibers  136  are generally bare, i.e., without an outer jacket, to facilitate miniaturization of the parallel optical device module  802 . However, when the parallel optical signal transceiver module is applied for a considerably long distance transmission and bare optical fibers are used, the bare optical fibers have a deteriorated mechanical strength so as to be weakened with respect to the outer environment. FIG. 8 shows an embodiment for improving this structure. 
     Optical transceiver module  802 , according to some embodiments of the present invention, are mounted on an interior printed circuit board  165  as described above for modules  300  (FIG. 2) and  500  (FIG.  5 ). Optical fiber array  136  connected thereto is bare without any jacket. A tip end of optical fiber array  136  is provided with an inner optical connector  193 . Further, inner optical connector  193  can be mounted on a housing  192  and coupled to an outer optical connector  194 . Base optical fibers of optical fiber array  136  are then coupled to jacketed optical fibers of jacketed optical fiber array  191 . Jacketed optical fiber array  191  provides for mechanical protection of optical fibers as well as environmental protection for optical fibers and is therefore suited for long-distance transmission of optical systems. 
     Some embodiments of optical transceiver modules according to the present invention include VCSEL light emitting devices in order to reduce power consumption and increase efficiency in coupling optical signals to optical fibers. A 45 degree slant-processed optical fiber array block can be utilized in coupling signals to optical fibers. A metal plate can be utilized in the case to rigidly position optical fibers relative to optical devices, protect components from external electromagnetic fields as well as environmental pollutants, and to provide a heat-sink. In some embodiments, the optical transceivers module can be miniaturized to have a height of about 1 to about 2 mm. 
     In addition, electrical connection parts of the modules can be formed in a detachable connector structure so that optical connection parts remain fixed, to thereby prevent a performance deterioration due to polluted optical connection parts. Further, some embodiments of the invention include a second optical coupler to a jacketed optical fiber array for long distance signal transmission and reception between systems. 
     The above disclosure provides examples of embodiments of the invention only and is not intended to be limiting. One skilled in the art will recognize variations which are intended to be within the scope of this invention. For example, other methods of coupling light to optical devices, e.g., with collimator, may be utilized. As such, the invention is limited only by the following claims.