Optical connector

An optical connector comprises two optical connector bodies, each carrying an optical element such as an optical fiber, a lens, an optical source or an optical detector. Each optical connector body has a guide formation extending in a direction transverse to the optical axis of its respective optical element and a stop means extending in a direction transverse to its respective guide formation. Sliding engagement of the guide formations guides relative movement of the connector bodies in a direction transverse to the optical axes to bring the stop means into engagement and the optical axes into alignment. The optical connector is particularly suited to optical interconnection of circuit boards slidably mounted in card guides.

The present invent to optical connectors. 
Terminal equipment for fiber optic communications systems includes 
electronic transmitter circuitry which drives an optical source, such as a 
laser diode, and electronic receiver circuitry which is fed by an optical 
detector, such as an avalanche photodiode. The electronic transmitter and 
receiver circuitry is electrically connected to other electronic terminal 
equipment, such as multiplexers, demultiplexers, and digital 
cross-connects. The optical source and detector are connected to an 
optical fiber which provides a transmission path between the terminal 
equipment and other similar terminal equipment at a remote location. 
The electronic circuitry, optical source and optical detector are typically 
mounted on printed circuit boards which are suitably received in card 
guides mounted to an equipment frame. A back plane mounted to the rear of 
the frame includes board edge connectors aligned with the card guides and 
electrical conductors interconnecting the board edge connectors. The 
circuit boards are provided with board edge electrical contacts which are 
received in the board edge connectors when the circuit boards are slidably 
inserted in the card guides to electrically connect the circuitry to the 
electrical conductors on the back plane. The electrical conductors provide 
the required electrical connections between circuit boards. 
The circuit boards also include optical connector parts which are optically 
coupled to the optical sources and to the optical detectors of the 
receivers and transmitters. The board mounted optical connector parts must 
be mated with frame mounted optical connector parts to optically connect 
the optical sources and the optical detectors to optical fibers 
terminating on the frame mounted optical connectors. 
Most optical connector parts are provided with screw or bayonet type 
fittings. Thus, the optical connector parts must be rotatably mated after 
the circuit boards are inserted and rotatably unmated before the circuit 
boards are withdrawn. The optical connector parts must be mounted where 
they are manually accessible when the circuit boards are mounted in the 
frame, for example at the front of the frame. This is not always 
convenient or possible, particularly when the frame carries a large number 
of densely packed circuit boards. Moreover, operators may forget to 
rotatably mate the optical connector parts when inserting a circuit board, 
leaving the circuit board optically disconnected, or may forget to 
rotatably unmate the optical connector parts when removing a circuit 
board, physically damaging the circuit board, connector parts or optical 
fibers. 
Some of the above problems have been overcome by providing back plane 
mounted optical connector parts which slidably receive circuit board 
mounted optical connector parts to effect an optical connection. In this 
case, a single circuit board insertion operation effects electrical 
connections by insertion of board edge electrical contacts into back plane 
mounted board edge electrical connectors and simultaneously effects 
optical connections by insertion of circuit board mounted optical 
connector parts into back plane mounted optical connector parts. 
Unfortunately, in the known board edge optical connector arrangements the 
circuit board mounted optical connector parts are mounted at leading edges 
of the circuit boards. These leading edges are already congested with 
board edge electrical contacts. Moreover, in the known board edge optical 
connector arrangements the frame mounted optical connector parts are 
mounted at the back plane which is already congested with electrical board 
edge connectors and electrical conductors. 
The present invention provides an optical connector which can be used to 
avoid some or all of the problems described above. 
One aspect of the invention provides an optical connector comprising: 
a first connector body carrying a first optical element having a first 
optical axis, the first connector body having a first guide formation 
extending in a direction transverse to the first optical axis and a first 
stop means extending in a direction transverse to the first guide 
formation; and 
a second connector body carrying a second optical element having a second 
optical axis, the second connector body having a second guide formation 
extending in a direction transverse to the second optical axis and a 
second stop means extending in a direction transverse to the second guide 
formation, sliding engagement of the first guide formation with the second 
guide formation guiding movement of the first connector body with respect 
to the second connector body in a direction transverse to the first and 
second optical axes to bring the first stop means into engagement with the 
second stop means and the first optical axis into alignment with the 
second optical axis. 
Alignment of the first and second optical axes effects an optical 
connection between the optical elements. One of the connector bodies may 
be mounted to a frame adjacent to a card guide and carry an optical 
element in the form of a lens optically coupled to an optical fiber. The 
other of the connector bodies may be mounted to a circuit board adjacent a 
side edge of the circuit board and carry an optical element in the form of 
another lens optically coupled to an optoelectronic device. Insertion of 
the circuit board into the card guide aligns the optical connector bodies 
to optically connect the optoelectronic device to the fiber via the 
lenses. 
The fiber may terminate at another frame mounted connector body for optical 
connection to an optoelectronic device on another circuit board. The other 
circuit board may be mounted in the same frame or in another frame with 
the fiber extending within a cable jacket between the two frames. 
Thus another aspect of the invention provides an assembly for electrical 
and optical interconnection of circuit boards, comprising: 
at least one frame comprising a plurality of card guides and an electrical 
back plane, the electrical back plane carrying a plurality of electrical 
board edge connectors and a plurality of electrical conductors 
interconnecting the board edge connectors, each board edge connector 
aligned with a respective pair of the card guides; 
a plurality of optical connector parts mounted to the frame forward of the 
electrical back plane and between the card guides; 
optical waveguide means interconnecting frame mounted optical connector 
parts; and 
a plurality of circuit boards slidably received in the card guides, the 
circuit boards having board edge electrical contacts on leading edges of 
the circuit boards and optical connector parts at side edges of the 
circuit boards, sliding insertion of the circuit boards into the card 
guides urging the board edge electrical contacts into the board edge 
connectors to electrically interconnect the circuit boards and aligning 
the board mounted optical connector parts with the frame mounted optical 
connector parts to optically interconnect the circuit boards. 
Hence, the invention provides an optical connector which can be used to 
effect optical connection upon insertion of a circuit board into a frame 
while avoiding congestion of a leading edge of the circuit board and 
avoiding congestion of a back plane of the frame by mounting the frame 
mounted optical connector part forwardly of the backplane between the card 
guides and by mounting the board mounted connector part adjacent a side 
edge of the circuit board. 
The optical elements carried by the connector bodies may be optical fibers, 
lenses, optical sources, optical detectors or any combination of these 
items. For example, both of the optical connector bodies may carry an 
optical element in the form of a lens which is optically coupled to a 
respective optical fiber, so that insertion of the circuit board into the 
card guide aligns the optical connector bodies to optically interconnect 
the optical fibers via the lenses. 
A plurality of optical elements having parallel optical axes may be carried 
by each optical connector body, alignment of the optical connector bodies 
bringing each optical element of on connector body into optical alignment 
with a respective optical element of the other connector body to make a 
plurality of optical connections.

Referring to FIG. 1, an assembly 100 for electrical and optical 
interconnection of circuit boards comprises a frame for supporting the 
circuit boards. The frame comprises four transverse frame members 110 
which define the top, bottom, front and rear of the frame, a plurality of 
card guides 112 mounted to the frame members 110 to span the frame from 
front to rear, and an electrical back plane 114 mounted to the frame 
members 110 to span the rear of the frame. The back plane 114 comprises a 
printed circuit board carrying a plurality of board edge connectors 116, 
each of which is aligned with a respective pair of the card guides 112 and 
a plurality of electrical conductors in the form of printed electrical 
conductor traces 118 interconnecting the board edge connectors 116. 
The assembly 100 further comprises a plurality of optical connector parts 
120 mounted to the card guides 112 forward of the electrical back plane 
114, and optical waveguide means in the form of optical fibers 130 
interconnecting the frame mounted optical connector parts 120. 
The assembly 100 also comprises a plurality of circuit boards 140 slidably 
received in the card guides 112. The circuit boards 140 have board edge 
electrical contacts 142 on leading edges 144 of the circuit boards, and 
optical connector parts 150 spaced forwardly of the leading edges 144 
adjacent side edges 146 of the circuit boards 140. 
Sliding insertion of the circuit boards 140 into the card guides 112 urges 
the board edge electrical contacts 142 into the board edge electrical 
connectors 116 to electrically interconnect the circuit boards, and aligns 
the optical connector parts 120, 150 in a direction transverse to the 
direction of insertion. This alignment of the optical connector parts 120, 
150 effects an optical connection as described below to optically 
interconnect the circuit boards 140. 
Referring to FIG. 2, the frame mounted optical connector parts 120 each 
comprise a connector body in the form of a plug member 121 carrying an 
optical element in the 
form of a graded index rod lens 122 having an optical axis A--A The plug 
member 121 has a guide formation in the form of external base and side 
surfaces 123, 124 which extend in a direction transverse to the optical 
axis A--A. A leading edge 125 of the plug member 121 is bevelled at the 
external base and side surfaces 123, 124. A trailing edge 126 of the plug 
member 121 is also bevelled at the external side surfaces 124. The 
bevelled leading edge 125 acts as a stop means and the bevelled trailing 
edge 126 coacts with latching means as described below. 
The plug member 121 further comprises resilient mounting means in the form 
of resiliently deformable arms 127 which join the plug member 121 to an 
adjacent card guide 112. The arms 127 are secured to the plug member 121 
by means of ball-in-socket joints 128. 
A free end 132 of one of the optical fibers 130 is secured by means of 
epoxy bonding on the optical axis A--A to optically couple the fiber 130 
to the lens 122. 
Referring to FIG. 3, the board mounted optical connector parts 150 each 
comprise a connector body in the form of a receptacle member 151. The 
receptacle member has a channel formation in the form of a base 152 and 
side walls 153 defining a channel 154. The base 152 of the channel 
formation carries an optical element in the form of a lens 157 having an 
optical axis B--B. The receptacle member 151 has a guide formation in the 
form of internal base and side surfaces 155, 156 of the channel 154 which 
extend in a direction transverse to the optical axis B--B. 
The receptacle member 151 has stop means in the form of a pair of stop 
elements, each stop element comprising a triangular spring 160 projecting 
inward from a respective recess 159 in a respective internal side surface 
156 of the channel 154. The triangular springs 160 are complementary to 
the bevelled leading edge 125 of the plug member 121. 
The receptacle member 151 also has opposed resilient means in the form of a 
pair of triangular springs 162 projecting inward from respective recesses 
159 in respective internal side surfaces 156 of the channel 154 at a 
location disposed between the stop element triangular springs 160 and a 
leading edge 164 of the receptacle member 151. The leading pair of 
triangular springs 162 act as releasable latching means as described 
below, and are complementary to the bevelled trailing edge 126 of the plug 
member 121. 
The receptacle member 151 further comprises rigid mounting means in the 
form of a rigid mounting foot 166 which is secured to the circuit board 
140 at a location spaced inwardly from the side edge 146 of the circuit 
board. 
The receptacle member 151 also carries an optoelectronic device 168, for 
example an optical source or an optical detector, on the optical axis 
B--B. The optoelectronic device 168 is optically coupled to the lens 157. 
When circuit boards 140 are inserted into card guides 112, the circuit 
boards slide rearward within the card guides until the leading edges 144 
of the circuit boards contact the back plane 114 and the board edge 
electrical contacts 142 enter the board edge electrical connectors 116 to 
electrically interconnect the circuit boards 140. 
Referring to FIGS. 4 and 5, as the circuit boards 140 slide rearward within 
the card guides 112, the optical connector receptable members 151 engage 
the optical connector plug members 121, the internal base and side 
surfaces 155, 156 of the receptacle members 151 slidably engaging the 
external base and side surfaces 123, 124 of the plug members 121 to guide 
the receptacle members 151 in a direction transverse to the optical axes 
A--A, B--B over the plug members 121. The bevelled leading edges 125 of 
the plug members 121 facilitate entry of the plug members 121 into the 
channels 154 of the receptacle members 151. 
As the receptacle members 151 slidably engage the plug members 121, the 
leading triangular springs 162 compress to permit sliding motion of the 
plug members 121 within the channels 154 as shown in FIG. 4(b). Once the 
leading triangular springs 162 have passed the trailing edges 126 of the 
plug members 121, they spring inward to inhibit sliding motion of the plug 
members 121 within the channels 154, thereby latching the plug members 121 
within the channels 154 of the receptacle members 151 as shown in FIG. 
4(c). At the same time, the stop element triangular springs 160 engage the 
bevelled leading edges 125 of the plug members 121 to fix the position of 
the plug members 121 within the channels 154. The resilient arms 127 
joining the plug members 121 to the card guides 112 deform as necessary to 
enable the plug members 121 to enter and take the desired position between 
the pairs of triangular springs 160, 162 within the channels 154. 
The distance between the external side surfaces 124 of the plug members 121 
and the optical axes A--A is substantially equal to the distance between 
the internal side surfaces 156 of the channels 154 and the optical axes 
B--B. The distance between the bevelled leading edges 125 of the plug 
members 121 and the optical axes A--A is substantially equal to the 
distance between the stop element triangular springs 157 and the optical 
axes B--B. As a result, when the plug members 121 are latched in position 
in the channels 154, the optical axes A--A are aligned in a direction 
transverse to the direction of insertion with the optical axes B--B, and 
the optical devices 168 are optically coupled to the fibers 130 via the 
lenses 122, 158. 
Of course, the outer dimensions of the plug member 121 must be very 
slightly smaller than the internal dimensions of the receptacle member 151 
to permit sliding movement of the plug member 121 within the channel 154. 
The triangular springs 160, 162 bias the plug member 121 both laterally 
and longitudinally to centre the plug member 121 both laterally and 
longitudinally within the channel 154 when the plug member 121 is latched 
to the receptacle member 151. The resilient arms 127 deform laterally and 
the ball-in-socket joints 128 swivel as necessary to permit such centering 
action. 
In order to ensure that plug member 121 is urged firmly against the 
receptacle member 151 in a direction parallel to the optical axes A, B, 
the plug member 121 is mounted slightly lower than the receptacle member 
151. As shown in FIG. 5(b), the bevelled leading edge 125 of the plug 
member 121 rides over the leading edge of the receptacle member 151 into 
the channel 154. The resilient arms 127 deform vertically and the 
ball-in-socket joints 128 swivel as necessary to permit such action. The 
resilient arms 127 urge the plug member 121 downward against the base 
surface 155 of the receptacle member 151 when the plug member 121 is 
latched to the receptacle member 151. 
Thus, the relative positions of the receptacle and plug members 121, 151 
and the lenses 122, 157 which they carry are completely determined in 
three dimensions when the plug member 121 is latched to the receptacle 
member 151. 
The members 121, 151 may be unlatched by pulling the circuit boards 140 
with sufficient force to compress the latching triangular springs 162. 
In the assembly 100, the members 121, 151 are mounted well forward of the 
back plane 114 and the leading edge 144 of the circuit board 140. This 
positioning of the members 121, 151 does not interfere with the placement 
of electrical board edge connectors 116 on the back plane 114 or with the 
placement of board edge contacts 142 on the circuit board 140. Moreover, 
the interconnecting fibers 130 are mounted well forward of the back plane 
114 so as to remain separate from electrical cables which may be connected 
to the back plane 114 for electrical connection of the frame to other 
frames. 
FIGS. 6 and 7 show connector parts of an optical connector according to a 
second embodiment. Referring to FIG. 6, a frame mounted optical connector 
part 220 comprises a connector body in the form of a plug member 221 
carrying a plurality of optical elements in the form of large core optical 
fibers 222 having parallel optical axes. The plug member 221 has a guide 
formation in the form of an external base surface 223 and an external side 
surface 224, both of which extend in a direction transverse to the optical 
axes. The external base surface 223 is inclined upward toward a leading 
edge 225 of the plug member 221 and the leading edge 22 of the plug member 
221 is bevelled at the side surface 224 to facilitate entry of the plug 
member 221 into a receptacle member as described below. The leading edge 
225 acts as a stop means as described below, and together with the base 
surface 223 and side surface 224 defines an external reference corner 226 
of the plug member 221. 
The plug member 221 further comprises resilient mounting means in the form 
of resiliently deformable arms 227 which join the plug member 221 to an 
adjacent card guide 212. The arms 227 are integrally joined to the plug 
member 221 in a manner which permits limited angular movement of the plug 
member 121 with respect to each arm 227 in planes parallel to and 
perpendicular to the card guide 212. 
Referring to FIG. 7, a board mounted optical connector part 250 comprises a 
connector body in the form of a receptacle member 251 having a channel 
formation in the form of a base 252 and side walls 253 defining a channel 
254. The base 252 carries a plurality of optical elements in the form of a 
large core optical fibers 258 having parallel optical axes. 
The receptacle member 251 has a guide formation in the form of an internal 
base surface 255 and an internal side surface 256 of the channel 254. 
These surfaces 255, 256 extend in a direction transverse to the optical 
axes of the large core optical fibers 258. 
The receptacle member 251 has stop means in the form of an end wall 260 
extending across the channel 254. Together with the base surface 255 and 
side surface 256, the end wall 260 defines an internal reference corner 
261 of the receptacle member 251. 
The receptacle member 251 further comprises rigid mounting means in the 
form of a rigid mounting foot 266 which is secured to a circuit board 240 
at a location spaced inwardly from a side edge 246 of the circuit board 
240. 
As shown in FIGS. 8 and 9, when circuit boards 240 are inserted into card 
guides 212 the circuit boards 240 slide rearward within the card guides 
212 until leading edges of the circuit boards contact a back plane and the 
board edge electrical contacts enter the board edge electrical connectors 
to electrically interconnect the circuit boards 240 as in the first 
embodiment. 
As the circuit boards 240 slide rearward within the card guides 212, the 
optical connector receptable members 251 engage the optical connector plug 
members 221, the internal base and side surfaces 255, 256 of the 
receptacle members 251 slidably engaging the external base and side 
surfaces 223, 224 of the plug members 221 to guide the receptacle members 
251 in a direction transverse to the optical axes of the large core fibers 
222, 258 over the plug members 221. The bevelled leading edges 225 of the 
plug members 221 facilitate entry of the plug members 221 into the 
channels 254 of the receptacle members 251. 
As the receptacle members 251 slidably engage the plug members 221, the end 
walls 260 of the channels 254 engage the leading edges 225 of the plug 
members 221 to fix the position of the plug members 221 within the 
channels 254. The resilient arms 227 joining the plug members 221 to the 
card guides 212 deform as necessary to enable the plug members 221 to 
enter and take the desired position within the channels 254. 
The plugs 221 are held in position within the channels 254 by the action of 
latching mechanisms (not shown) which latch the circuit boards 240 in 
position within the card guides 212 combined with the action of the 
resilient arms 227 which urge the external reference corners 226 of the 
plug members 221 firmly into the internal reference corners 261 of the 
receptacle members 251. As shown in FIGS. 8 and 9, the plug members 221 
are positioned on the card guides 212 and the receptacle members 251 are 
positioned on the circuit boards in positions which ensure that resilient 
arms 227 must deform upward, sideways and rearward. This ensures that the 
external reference corners 226 are firmly urged downward, sideways and 
forward into the internal reference corners 261 when the circuit boards 
240 are latched in place. 
The distance between the external side surfaces 224 of the plug members 221 
and the optical axes of the large core fibers 222 is substantially equal 
to the distance between the internal side surfaces 256 of the channels 254 
and the optical axes of the large core fibers 258. The distance between 
the leading edges 225 of the plug members 221 and the optical axes of the 
large core fibers 222 is substantially equal to the distance between the 
end wall 258 of the channel 258 and the optical axes of the large core 
fibers 258. As a result, when the plug members 221 are held in position in 
the channels 254, the optical axes of the large core fibers 222 are 
aligned in a direction transverse to the direction of insertion with the 
optical axes of the fibers 258 to optically couple each large core fiber 
222 to a respective large core fiber 258. 
Numerous modifications of the embodiments described above will be apparent 
to those skilled in the optical interconnection art. For example, plug 
members 320 could be mounted to circuit boards to mate with frame mounted 
receptacle members 350 as shown in FIG. 10. Receptacle members 450 could 
be resiliently mounted to mate with rigidly or resiliently mounted plug 
members 420 as shown in FIG. 10. The leading edges of receptacle members 
350, 450, 550 could be bevelled to facilitate entry of plug members 320, 
420, 520 into the receptacle members 350, 450, 550 as shown in FIG. 10. 
Moreover, connector bodies 320, 420, 520 could be mounted adjacent to both 
side edges on both surfaces of circuit boards to cooperate with connector 
bodies 350, 450, 550 on both sides of both card guides holding each board, 
thereby providing four connector bodies per circuit board as shown in FIG. 
10. Each connector body could extend virtually the entire length of its 
circuit board and carry a very large number of optical elements in one or 
more rows or arrays. Thus, an enormous number of optical connections could 
be provided for each circuit board without congesting the leading edge of 
the circuit board or the back plane of the frame. 
The frame mounted connector bodies could be mounted to parts of the frame 
other than the card guides, for example top and bottom planes of each 
shelf. FIG. 10 shows a connector body 550 mounted to a bottom plane 575 of 
a shelf. 
Indeed, frames could be supplied with optical connector bodies already in 
place as "optical shelves". Alternatively, "optical connection planes" 
comprising card guides and connector bodies could be supplied for assembly 
into "optical shelves". 
The modifications described above are within the scope of the invention as 
claimed below.