Optical module and optical transmission device

An optical module includes a substrate, a package, and a flexible substrate. The substrate is provided with an electrode. The package includes a housing fixed to the substrate, a receiving unit that optically demodulates a received optical signal to convert the optical signal into a reception electrical signal, an output terminal that is provided on a surface of the housing and outputs the reception electrical signal, an input terminal that is provided at a height from the substrate different from a height of the output terminal and receives a transmission electrical signal, and a transmitting unit that optically modulates the transmission electrical signal received from the input terminal and transmits an optical signal resulting from optical modulation. A flexible substrate has flexibility and includes a signal electrode that connects one of the output terminal and the input terminal to the electrode arranged on the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-201566, filed on Oct. 9, 2015, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to an optical module and an optical transmission device.

BACKGROUND

With the development of downsized optical modules including an optical modulator, for example, and that mutually convert electrical signals and optical signals, there have been increasing demands for downsized optical transmission devices that transmit and receive optical signals. Furthermore, there have also been increasing demands for large-capacity optical transmission devices having a baud rate of 64G baud, for example.

Examples of such optical transmission devices include, but are not limited to, optical transmission devices that perform coherent optical communications. The optical transmission devices that perform coherent optical communications transmit and receive two polarized-wave components of light from a light source with an I-channel signal and a Q-channel signal superimposed thereon, for example. The optical transmission devices have high-speed signal connections of four channels for transmission and four channels for reception, that is, a total of eight channels. In a case where differential signals are used as the I-channel signal and the Q-channel signal, the number of high-speed signal connections is 16 channels, which is twice as many as eight channels.

As described above, the optical transmission devices have high-speed signal connections of a number of channels. Therefore, the optical transmission devices may be downsized by integrating the transmission function and the reception function into a single optical module.

The optical module in which the transmission function and the reception function are integrated has large cross talk between wiring. Specifically, the optical module includes terminals corresponding to eight channels or 16 channels. The wiring connected to the terminals transmits high-speed signals of 32G baud or higher, for example. As a result, a number of terminals and wiring that transmit the high-speed signals are arranged close to each other, thereby causing cross talk.

Power of transmission electrical signals received by the optical module is substantially ten times the magnitude of power of reception electrical signals output from the optical module. In a case where the terminals and the wiring for the transmission electrical signals are arranged close to those for the reception electrical signals, cross talk caused by the transmission electrical signals serves as noise not negligible for the reception electrical signals.

SUMMARY

According to an aspect of an embodiment, an optical module includes: a substrate on which an electrode is arranged; a package; and a flexible substrate. The package includes: a housing fixed to the substrate; a receiving unit that optically demodulates a received optical signal to convert the optical signal into a reception electrical signal; an output terminal that is provided on a surface of the housing and that outputs the reception electrical signal obtained by the receiving unit; an input terminal that is provided at a height from the substrate different from a height of the output terminal and that receives a transmission electrical signal; and a transmitting unit that optically modulates the transmission electrical signal received from the input terminal and transmits an optical signal resulting from optical modulation. The flexible substrate has flexibility and includes a signal electrode that connects a first terminal of the output terminal and the input terminal to the electrode arranged on the substrate.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be explained with reference to accompanying drawings. The embodiments are not intended to limit the present invention.

[a] First Embodiment

FIG. 1is a front schematic of a configuration of an optical module100according to a first embodiment. The optical module100illustrated inFIG. 1includes a printed circuit board (PCB)110, a package120, optical fibers130, and a flexible printed circuit (FPC)140. The optical module100converts transmission electrical signals received from a driver, which is not illustrated, into optical signals and transmits them. The optical module100also converts received optical signals into reception electrical signals and outputs them.

The PCB110is a glass epoxy board, for example, and is a part serving as a board on which various parts constituting the optical module are mounted. The surface layer of the PCB110can be provided with printed electrodes that electrically connect the various parts. An inner layer of the PCB110is provided with a ground electrode111having a ground voltage. The ground electrode111is connected to ground electrodes on the surface layer of the PCB110.

The package120accommodates parts that mutually convert electrical signals and optical signals in one housing. Specifically, the package120includes a transmitting chip and a receiving chip in the housing fixed to the PCB110. The transmitting chip modulates light from a light source with the transmission electrical signals to generate optical signals. The receiving chip demodulates received optical signals to generate the reception electrical signals.

Output leads121athat output the reception electrical signals generated by the receiving chip protrude from the lower front surface of the housing of the package120. The output leads121afor two channels are provided because differential signals of an I-channel and a Q-channel are output as the reception electrical signals. The output leads121aof the respective channels are sandwiched between ground leads121bconnected to the ground electrodes. In other words, two output leads121aare arranged between the ground leads121bon the left end and at the center and the ground leads121bon the right end and at the center. The leads121aand121bare soldered to the signal electrodes and the ground electrodes, respectively, printed on the surface layer of the PCB110. In other words, the output leads121aare soldered to the signal electrodes, and the ground leads121bare soldered to the ground electrodes.

Input leads122athat transmit the transmission electrical signals to the transmitting chip protrude from the upper front surface of the housing of the package120. In other words, the input leads122aare provided at positions higher than those of the output leads121a. The input leads122afor two channels are provided because differential signals of the I-channel and the Q-channel are input as the transmission electrical signals. The input leads122aof the respective channels are sandwiched between ground leads122bconnected to the ground electrodes. In other words, two input leads122aare arranged between the ground leads122bon the left end and at the center and the ground leads122bon the right end and at the center. The leads122aand122bextend through the through holes in the FPC140, which will be described later, and are soldered to signal electrodes and ground electrodes, respectively, provided on the FPC140.

The optical fiber130transmits and receives optical signals to and from another optical transmission device, for example. In other words, the optical fiber130transmits optical signal output from the package120to another optical transmission device, for example. The optical fiber130transmits optical signals transmitted from another transmission device, for example, to the package120.

The FPC140is a flexible substrate having flexibility and supplies the transmission electrical signals output from the driver, which is not illustrated, to the package120. In other words, the FPC140includes a plurality of signal electrodes and a plurality of ground electrodes and transmits the transmission electrical signals to the package120via the signal electrodes. Specifically, the signal electrodes and the ground electrodes of the FPC140are soldered to the signal electrodes and the ground electrodes, respectively, on the surface layer of the PCB110on one end of the FPC140. The through holes through which the leads122aand122bof the package120extend are formed on the other end of the FPC140. The signal electrodes and the ground electrodes of the FPC140are soldered to the leads122aand122b, respectively. In other words, the signal electrodes are soldered to the input leads122a, and the ground electrodes are soldered to the ground leads122b.

The signal electrodes are provided on the surface of the FPC140farther from the package120, whereas the ground electrodes are provided on the surface of the FPC140closer to the package120. In other words, the signal electrodes and the ground electrodes of the FPC140serve as a micro-strip line.

FIGS. 2A and 2Bare side schematics of the configuration of the optical module100according to the first embodiment.FIG. 2Ais a schematic of connection of a signal electrode. As illustrated inFIG. 2A, the output lead121athat outputs the reception electrical signals protrudes from the lower portion of the package120and is soldered to a signal electrode112aon the surface layer of the PCB110. The input lead122athat receives the transmission electrical signals protrudes from the upper portion of the package120, extends through the through hole of the FPC140, and is soldered to the signal electrode of the FPC140. The signal electrode of the FPC140is provided on the surface of the FPC140farther from the package120. The upper end and the lower end of the FPC140are provided with pads (or lands) extending to both surfaces of the FPC140. The signal electrode is connected to the pad (or the land).

The pad on the lower end of the FPC140is soldered to a signal electrode113aon the surface layer of the PCB110. With this configuration, the transmission electrical signals output from the driver, which is not illustrated, are received by the package120via the signal electrode113aand the signal electrode of the FPC140. The output lead121afor the reception electrical signals and the input lead122afor the transmission electrical signals are separately provided at different heights from the PCB110. This configuration can reduce cross talk occurring near the input and output terminals of the package120.

FIG. 2Bis a schematic of connection of a ground electrode. As illustrated inFIG. 2B, the ground lead121bthat sandwiches the output leads121aprotrudes from the lower portion of the package120and is soldered to a ground electrode112bon the surface layer of the PCB110. The ground lead122bthat sandwiches the input leads122aprotrudes from the upper portion of the package120, extends through the through hole of the FPC140, and is soldered to the ground electrode of the FPC140. The ground electrode of the FPC140is provided on the surface of the FPC140closer to the package120. The upper end and the lower end of the FPC140are provided with pads (or lands) extending to both surfaces of the FPC140. The ground electrode is connected to the pad (or the land).

The pad on the lower end of the FPC140is soldered to a ground electrode113bon the surface layer of the PCB110. The ground electrodes112band113bare connected to the ground electrode111arranged in the inner layer of the PCB110. With this configuration, the surface of the FPC140closer to the package120is covered with the ground electrode having a ground voltage. The ground electrode can shield the signal electrode of the FPC140from the signal electrode112aon the surface layer of the PCB110. As a result, this configuration can reduce cross talk occurring between the transmission electrical signals transmitted by the signal electrode of the FPC140and the reception electrical signals transmitted by the signal electrode112aon the surface layer of the PCB110.

As illustrated inFIG. 1andFIGS. 2A and 2B, the output lead121aand the input lead122aare separately provided at different heights from the PCB110on the front surface of the housing of the package120. With this configuration, the wiring for the transmission electrical signals can be separated from the wiring for the reception electrical signals. Even when the power of the transmission electrical signals is large, this configuration can reduce cross talk occurring in the wiring for the reception electrical signals. Furthermore, the leads having especially large cross talk are spatially separated, thereby suppressing cross talk more reliably. As a result, this configuration can reduce noise in the reception electrical signals caused by cross talk due to the transmission electrical signals.

FIG. 3is a plan schematic of the configuration of the optical module100according to the first embodiment. As illustrated inFIG. 3, the package120includes a receiving chip124and a transmitting chip125mounted on a carrier123. The receiving chip124includes an optical demodulator, and the transmitting chip125includes an optical modulator.

The receiving chip124receives optical signals transmitted by the optical fiber130. The receiving chip124optically demodulates the optical signals to convert them into reception electrical signals and outputs the reception electrical signals to the output leads121a. By contrast, the transmitting chip125optically modulates the transmission electrical signals received from the input leads122ato convert them into optical signals and outputs the optical signals to the optical fiber130. Because the input leads122aare provided at positions higher than those of the output leads121aof the package120, the transmitting chip125is arranged at a position higher than that of the receiving chip124. Wiring that connects the receiving chip124and the output leads121ais provided in an inner layer of the carrier123so as to extend under the transmitting chip125. With this configuration, the transmitting chip125can be positioned closer to the leads than the receiving chip124. This configuration can shorten the wiring that transmits the transmission electrical signals in the package120. As a result, this configuration can reduce transmission loss of the transmission electrical signals and broaden the transmission band.

The output leads121aconnected to the receiving chip124are directly soldered to the respective signal electrodes112aon the surface layer of the PCB110. By contrast, the input leads122aconnected to the transmitting chip125are soldered to the respective signal electrodes of the FPC140at the through holes formed on one end of the FPC140. The signal electrodes of the FPC140are soldered to the respective signal electrodes113aon the surface layer of the PCB110on the other end of the FPC140.

As described above, the input leads of the package according to the present embodiment are provided at positions higher than those of the output leads. The output leads are directly soldered to the PCB, whereas the input leads are connected to the PCB via the FPC. With this configuration, the input terminals of the package can be spatially separated from the output terminals. As a result, this configuration can suppress cross talk occurring between the wiring that transmits the transmission electrical signals and the wiring that transmits the reception electrical signals.

As illustrated inFIGS. 2A and 2BandFIG. 3, a first end of the FPC140according to the first embodiment is soldered to the signal electrodes113aand the ground electrodes113bon the surface layer of the PCB110at a position farther from the package120. Alternatively, the first end of the FPC140may be soldered to the signal electrodes113aand the ground electrodes113bon the surface layer of the PCB110at a position closer to the package120. In this case, the FPC140may extend along the front surface of the housing of the package120. Even if the FPC140extends along the front surface of the housing of the package120, cross talk occurring between the input leads and the output lead can be reduced because the leads having especially large cross talk are separated.

[b] Second Embodiment

A second embodiment overlaps the positions of the input leads and the output leads in the array direction, thereby downsizing the package.

FIG. 4is a front schematic of a configuration of an optical module200according to the second embodiment. InFIG. 4, the same components as those inFIG. 1are denoted by same reference numerals, and explanation thereof will be omitted. The optical module200illustrated inFIG. 4includes a package210and an FPC220instead of the package120and the FPC140, respectively, of the optical module100illustrated inFIG. 1.

The package210includes a transmitting chip and a receiving chip. The transmitting chip modulates light from a light source with the transmission electrical signals to generate optical signals. The receiving chip demodulates received optical signals to generate the reception electrical signals. The output leads121aand the ground leads121bprotrude from the lower front surface of the housing of the package210and are soldered to the respective electrodes on the surface layer of the PCB110.

Input leads211athat transmit the transmission electrical signals to the transmitting chip protrude from the upper front surface of the housing of the package210. In other words, the input leads211aare provided at positions higher than those of the output leads121a. The input leads211afor two channels are provided because differential signals of the I-channel and the Q-channel are input as the transmission electrical signals. The input leads211aof the respective channels are sandwiched between ground leads211bconnected to the ground electrodes. In other words, two input leads211aare arranged between the ground leads211bon the left end and at the center and the ground leads211bon the right end and at the center. The leads211aand211bextend through the through holes in the FPC220, which will be described later, and are soldered to signal electrodes and ground electrodes, respectively, provided on the FPC220.

A plurality of leads121aand121band a plurality of leads211aand211bare separately provided at different heights from the PCB110on the front surface of the housing of the package210. The arrangement range of the leads121aand121b, however, overlap with that of the leads211aand211bin a direction parallel to the surface of the PCB110. In other words, at least part of the leads211aand211bare arranged above at least part of the leads121aand121bin an overlapping manner.

As described above, the leads211aand211barranged at the upper portion of the package210overlap with the leads121aand121barranged at the lower portion of the package210. This configuration can reduce the width of the package120in the direction parallel to the surface of the PCB110. In other words, this configuration can downsize the package120.

The FPC220is a flexible substrate having flexibility and supplies the transmission electrical signals output from a driver, which is not illustrated, to the package210. In other words, the FPC220includes a plurality of signal electrodes and a plurality of ground electrodes and transmits the transmission electrical signals to the package210via the signal electrodes. Specifically, the signal electrodes and the ground electrodes of the FPC220are soldered to the signal electrodes and the ground electrodes, respectively, on the surface layer of the PCB110on one end of the FPC220. Through holes through which the leads211aand211bof the package210extend are formed on the other end of the FPC220. The signal electrodes and the ground electrodes of the FPC220are soldered to the leads211aand211b, respectively. In other words, the signal electrodes are soldered to the input leads211a, and the ground electrodes are soldered to the ground leads211b.

The signal electrodes of the FPC220extend in a direction away from the leads121aand121bas they extend from the upper end to the lower end of the FPC220. This is because the signal electrodes that transmit the transmission electrical signals and the signal electrodes that transmit the reception electrical signals are printed side by side on the surface layer of the PCB110while the leads211aand211bare arranged in a manner overlapping with the leads121aand121b. In other words, the signal electrodes and the ground electrodes printed on the surface layer of the PCB110correspondingly to the leads211aand211b, respectively, are positioned farther from the leads121aand121bthan the positions just under the leads211aand211b.

As described above, the input leads of the package according to the present embodiment are provided at positions higher than those of the output leads. Furthermore, the arrangement range of the input leads overlap with that of the output leads in a direction parallel to the surface of the PCB. This configuration can reduce the width of the package in the direction parallel to the surface of the PCB, thereby downsizing the package.

The configuration illustrated inFIG. 4prevents the wiring that transmits the transmission electrical signals from overlapping with the wiring that transmits the reception electrical signals by changing the shape of the signal electrodes of the FPC220that transmit the transmission electrical signals. Alternatively, it is also possible to prevent both of the wiring from overlapping with each other by changing the shape of the signal electrodes that transmit the reception electrical signals.

FIG. 5is a plan schematic of another configuration of the optical module200according to the second embodiment. InFIG. 5, the same components as those inFIGS. 1 and 4are denoted by same reference numerals, and explanation thereof will be omitted. The optical module200illustrated inFIG. 5includes the FPC140identical with that of the optical module100illustrated inFIG. 1instead of the FPC220of the optical module200illustrated inFIG. 4. Signal electrodes231that transmit the reception electrical signals are printed on the surface layer of the PCB110.

As illustrated inFIG. 5, the signal electrodes231extend in a direction away from the input leads211aas they extend away from the output leads121a. Specifically, the FPC140extends in a direction away from the package210as it extends from the input leads211aarranged on the upper end to the lower end. The signal electrodes231are sufficiently away from the input leads211aoutside the projection range of the FPC140onto the surface of the PCB110. This is because the signal electrodes that transmit the transmission electrical signals and the ground electrodes can be provided on the FPC140within the projection range of the FPC140onto the surface of the PCB110. As a result, the signal electrodes that transmit the reception electrical signals can be printed on the surface layer of the PCB110. In other words, the signal electrodes that transmit the transmission electrical signals are printed on the surface layer of the PCB110outside the projection range of the FPC140onto the surface of the PCB110. As a result, the signal electrodes231are printed at the positions sufficiently away from the signal electrodes.

By changing the shape of the signal electrodes231that transmit the reception electrical signals as described above, the FPC140having a smaller width than that of the FPC220can be used. As a result, this configuration can downsize the package and the FPC.

As illustrated inFIGS. 6 and 7, signal electrodes241may be provided in an inner layer of the PCB110. In other words, the signal electrodes113athat transmit the transmission electrical signals are provided on the surface layer of the PCB110, and the signal electrodes241that transmit the reception electrical signals are provided in the inner layer of the PCB110. The signal electrodes241are arranged in a layer different from that of the ground electrode111provided in an inner layer of the PCB110.

As described above, the signal electrodes241that transmit the reception electrical signals are provided in an inner layer of the PCB110. This configuration allows the signal electrodes113athat transmit the transmission electrical signals to overlap with the signal electrodes241that transmit the reception electrical signals, thereby downsizing the PCB besides the package and the FPC.

A third embodiment thickens the ground leads connected to the FPC and increases the number thereof to prevent breaking of the signal electrodes of the FPC.

FIG. 8is a front schematic of a configuration of an optical module300according to the third embodiment. InFIG. 8, the same components as those inFIG. 1are denoted by same reference numerals, and explanation thereof will be omitted. The optical module300illustrated inFIG. 8includes a package310and an FPC320instead of the package120and the FPC140, respectively, of the optical module100illustrated inFIG. 1.

The package310includes a transmitting chip and a receiving chip. The transmitting chip modulates light from a light source with the transmission electrical signals to generate optical signals. The receiving chip demodulates received optical signals to generate the reception electrical signals. The output leads121aand the ground leads121bprotrude from the lower front surface of the housing of the package310and are soldered to the respective electrodes on the surface layer of the PCB110.FIG. 8illustrates the output leads121aand the ground leads121bfor one channel alone.

Input leads311athat transmit the transmission electrical signals to the transmitting chip protrude from the upper front surface of the housing of the package310. In other words, the input leads311aare provided at positions higher than those of the output leads121a. The input leads311afor two channels are provided because differential signals of the I-channel and the Q-channel are input as the transmission electrical signals. The input leads311aof the respective channels are sandwiched between ground leads311bconnected to the ground electrodes. In other words, two input leads311aare arranged between pairs of ground leads311baligned in the height direction on the left end and at the center and pairs of ground leads311bon the right end and at the center.

The ground leads311baccording to the present embodiment have a larger diameter than that of the input leads311a. Two ground leads311bprotrude from the front surface of the housing of the package310in a manner aligned in the height direction. The pairs of ground leads311bprotrude from three positions at substantially the same height on the front surface of the housing of the package310. The input leads311aprotrude between the pairs of ground leads311b. As illustrated inFIG. 8, a total of four input leads311aare provided, whereas a total of six ground leads311bare provided, which is larger than the total of the input leads311a.

As described above, a larger number of ground leads311bhaving a larger diameter are soldered to the respective ground electrodes at the through holes formed in the FPC320. With this configuration, the FPC320is less likely to be bent at the height where the ground leads311bare arranged. As a result, portions near the connections between the input leads311aand the signal electrodes of the FPC320are less likely to be bent, thereby preventing breaking of the signal electrodes.

As described above, the ground leads connected to the FPC according to the present embodiment have a larger diameter than that of the input leads. Two ground leads are aligned in the height direction of the package, and the input leads are arranged between the pairs of ground leads. This configuration reinforces the connection between the ground leads and the FPC, thereby suppressing bend of the FPC at the connections between the input leads and the signal electrodes of the FPC. As a result, this configuration can prevent breaking at the connections between the input leads and the signal electrodes of the FPC.

The third embodiment may simply make the diameter of the ground leads311blarger than that of the input leads311aor may simply increase the number of ground leads311b. In both cases, the connection between the ground leads311band the FPC is reinforced. As a result, the FPC320is less likely to be bent, thereby preventing breaking.

A fourth embodiment includes a ceramic substrate exposed outside from the package, and the FPC is soldered to terminals on the ceramic substrate. With this configuration, the fourth embodiment makes the pitch between the terminals smaller, thereby downsizing the package.

FIG. 9is a side schematic of a configuration of an optical module400according to the fourth embodiment. InFIG. 9, the same components as those inFIG. 1are denoted by same reference numerals, and explanation thereof will be omitted. The optical module400illustrated inFIG. 9includes a package410and an FPC420instead of the package120and the FPC140, respectively, of the optical module100illustrated inFIG. 1.

The package410has a transmitting chip and a receiving chip. The transmitting chip modulates light from a light source with the transmission electrical signals to generate optical signals. The receiving chip demodulates received optical signals to generate the reception electrical signals. A ceramic substrate411is exposed from the front surface of the housing of the package410, and an input terminal412connected to the transmitting chip is provided on the upper surface of the ceramic substrate411. An output lead413connected to the receiving chip protrudes from the lower portion of the ceramic substrate411and is soldered to a signal electrode on the surface layer of the PCB110. InFIG. 9, the signal electrode to which the output lead413is soldered is connected to wiring in an inner layer of the PCB110because the reception electrical signals are transmitted by the wiring in the inner layer of the PCB110.

The FPC420is a flexible substrate having flexibility and supplies the transmission electrical signals output from a driver, which is not illustrated, to the package410. In other words, the FPC420includes a plurality of signal electrodes and a plurality of ground electrodes and transmits the transmission electrical signals to the package410via the signal electrodes. Specifically, the signal electrodes and the ground electrodes of the FPC420are soldered to the signal electrodes and the ground electrodes, respectively, on the surface layer of the PCB110on one end of the FPC420. The signal electrodes are directly soldered to the input terminals412provided on the upper surface of the ceramic substrate411on the other end of the FPC420. Similarly, the ground electrodes of the FPC420are directly soldered to the terminals provided on the upper surface of the ceramic substrate411. With this configuration, the FPC420requires no through hole or no land around through holes, thereby making the pitch between the terminals corresponding to the signal electrodes and the ground electrodes smaller. As a result, this configuration can reduce the width of the package410in the depth direction inFIG. 9.

As described above, the present embodiment includes the input terminals on the upper surface of the ceramic substrate exposed outside from the package and the output lead provided on the lower portion of the ceramic substrate. The signal electrodes of the FPC are directly soldered to the input terminals on the upper surface of the ceramic substrate. With this configuration, the FPC requires no through hole through which the input leads extend, thereby making the pitch between the input terminals smaller. As a result, this configuration can downsize the package.

The signal electrodes according to the fourth embodiment may be arranged on the surface of the FPC420closer to the package410or the surface farther from the package410. In both cases, a pad provided on an end of the FPC420enables the soldering of the signal electrodes of the FPC420to the input terminals provided on the upper surface of the ceramic substrate411.

In a case where the signal electrodes are arranged on the surface of the FPC420farther from the package410, the surface closer to the package410can be covered with the ground electrodes. With this configuration, the ground electrodes shield the signal electrodes of the FPC420that transmit the transmission electrical signals from the signal electrodes on the surface layer of the PCB110that transmit the reception electrical signals, thereby reducing cross talk.

Furthermore, the ground electrodes covering the surface of the FPC420closer to the package410may be covered with a resin coverlay, for example. This configuration can further reduce cross talk.

The input and output terminals for electrical signals and the optical fibers130according to the embodiments above are connected to respective adjacent side surfaces of the package. The positional relation between the input and output terminals for electrical signals and the optical fibers130, however, may vary depending on the configuration of the transmitting chip and the receiving chip and the design conditions for the optical module.

As illustrated inFIG. 10, for example, the output leads121afor the reception electrical signals and the input leads122afor the transmission electrical signals and the optical fibers130may be connected to respective facing side surfaces of the package120. Alternatively, as illustrated inFIG. 11, for example, the output leads121afor the reception electrical signals and the input leads122afor the transmission electrical signals and the optical fibers130may be connected to a single side surface of the package120by changing the traveling direction of the optical signals with prisms126provided in the package120. InFIGS. 10 and 11, the same components as those inFIG. 3are denoted by same reference numerals.

While the input terminals that receive the transmission electrical signals according to the embodiments above are provided at positions higher than those of the output terminals that output the reception electrical signals on the front surface of the housing of the package, the output terminals may be provided at positions higher than those of the input terminals. In this case, the positional relation between the receiving chip124and the transmitting chip125in the package may be opposite to that described in the embodiments above. Similarly, the signal electrodes that transmit the transmission electrical signals may be arranged in an inner layer of the PCB110, and the signal electrodes that transmit the reception electrical signals may be arranged on the surface layer of the PCB110.

The optical modules according to the embodiments above are applicable to an optical transmission device that transmits and receives optical signals, for example.FIG. 12is a block diagram of an exemplary configuration of an optical transmission device500.

As illustrated inFIG. 12, the optical transmission device500includes a data generating circuit510, an optical module520, and a data receiving circuit550. The optical module520includes a driver530and a package540.

The data generating circuit510generates transmission data and outputs it to the optical module520. The transmission data output to the optical module520is received by the driver530in the optical module520. The driver530generates transmission electrical signals based on the transmission data. The transmission electrical signals are supplied from the driver530to the package540, and the package540performs optical modulation based on the transmission electrical signals.

By contrast, optical signals received by the package540from the optical fiber are optically demodulated by the package540. Reception electrical signals resulting from optical demodulation are output to the data receiving circuit550. The data receiving circuit550demodulates and decodes the reception electrical signals, thereby generating reception data.

As described above, the package540includes a transmitting chip that performs optical modulation and a receiving chip that performs optical demodulation. The package540further includes input terminals and output terminals. The input terminals receive the transmission electrical signals from the driver530, and the output terminals output the reception electrical signals to the data receiving circuit550. As described in the embodiments above, the input terminals and the output terminals are separately provided at different heights from the substrate on the package540. With this configuration, the wiring that transmits the transmission electrical signals is spatially separated from the wiring that transmits the reception electrical signals. As a result, this configuration can suppress cross talk occurring between the wiring.

According to an embodiment of the optical module and the optical transmission device, cross talk can be suppressed.