Integration of laser sources and detectors for a passive optical network

IS 2 365 486 T3

DESCRIPTION

Integration of laser sources and detectors for a passive optical network

Field

Embodiments of the invention generally relate to optical networks. More particularly, one aspect of an embodiment of the invention relates to a laser emitting capable optical gain media array that is contained in a single integral unit.

Background

Fiber optic systems typically transmit optical signals back and forth between a central office and a multitude of residential and business locations. Each residential or business location can be assigned a narrow bandwidth of wavelengths or channel within a global optical signal to communicate to and from the central office. As the number of subscribers using that fiber optic system increases, the number of components in the central office can increase to transmit and receive optical signals from those subscribers.

US 2003/0142798 refers to a wavelength division multiplexed passive optical network. In particular, it relates to a technology for minimizing optical loss in a wavelength division multiplexed passive optical network based on a wavelength clamp light source. Thus, it improves the transmission quality and increases the transmission distance. The described 4-port optical path setting device increases the amount of light injected into an optical transmitter and thereby improves the wavelength setting characteristic of a light source. Furthermore, this can decrease the optical transmission loss in an optical transmission path and by means of an optical amplifier inserted into it; it can also compensate for optical loss in an optical transmission path. A 4-port optical path establishment device having these characteristics and a method for failover without additional optical loss is presented.

WO 99/337002 describes an array of semiconductor reflector optical amplifiers that can be constructed in a monolithic fashion connected to a WDM multiplexer and a wavelength reflector.

Summary

Various methods and apparatus are described in which a laser emitting capable optical gain media array is contained in a single integral unit. The array contains four or more optical gain media with laser emission capability. Each laser-capable optical gain medium supplies a separate optical signal containing a different wavelength band from other laser-capable optical gain medium in the array to a first multiplexer / demultiplexer. There is a connection for an outgoing fiber to route an optical signal to and from a passive optical network.

According to a first aspect of the present invention, there is provided an apparatus according to claim 1.

According to a second aspect of the present invention, there is provided a method according to claim 10.

Other features and advantages of the present invention will be apparent from the accompanying drawings and the description that follows.

Brief description of the drawings

The present invention is illustrated as an example and is not limited to the figures of the attached drawings, in which like references indicate similar elements and in which:

Figure 1 illustrates a block diagram of one embodiment of a multi-wavelength optical gain media array with laser emission capability.

Figure 2 illustrates a block diagram of an embodiment of an array of four or more feedback lasers distributed in an integral unit. Coupled each array of four or more distributed feedback lasers 202 to a power splitter 212.

Figure 3 illustrates a block diagram of one embodiment of a laser array and a broadband light source for supplying an optical signal to each of the lasers all contained in an integral unit.

IS 2 365 486 T3

Figure 4 illustrates a block diagram of an embodiment of an array of four or more optical receivers and a multiplexer / demultiplexer integrated into a single integral unit.

Figure 5 illustrates a block diagram of one embodiment of an optical gain media array with laser emission capability and an array of optical receivers contained in an integral unit.

Figure 6 illustrates a block diagram of one embodiment of a laser array and an optical receiver array in one integral unit.

Detailed explanation

In general, various methods and apparatus are described in which an array of laser-capable optical gain media and an array of optical receivers are included in a single integral unit. The array may contain four or more optical gain media with laser emission capability. Each laser-capable optical gain medium supplies a separate optical signal containing a band of different wavelengths than the other laser-capable optical gain means in the array to a first multiplexer / demultiplexer. Similarly, a second multiplexer / demultiplexer can route the optical signals to the array of optical receivers. There is a connection for an outgoing fiber to route an optical signal to and from a passive optical network.

Figure 1 illustrates a block diagram of one embodiment of a multi-wavelength optical gain media array with laser emission capability. The planar light wave circuit 100 may contain an array of more than four laser-capable optical gain media 102, such as lasers, a multiplexer / demultiplexer 112, an optical amplifier 104, a band wavelength reflector wide 106, an electrical modulation source 108, a connection 110 to an output fiber, and an output fiber 114 going to a passive wavelength division multiplexed optical network.

Multiple laser emitting capable optical gain means 102, such as a first gain means 116 to an N-th gain means 118, may exist in planar light circuit 100. Each gain means 102 provides an optical signal that it has a narrow band of wavelengths (λ) different from the other gain media. Each of the gain means 102 is coupled to its own port on the multiplexer / demultiplexer 112. The broadband wavelength reflector 106 is coupled to the output of the multiplexer / demultiplexer 112. The wavelength reflector 106 routes a portion of each optical signal as a regenerative feedback through the multiplexer / demultiplexer 112 to the gain medium. 102 that supplied the optical signal.

Modulation source 108 may provide a data signal to gain means matrix 102 to directly modulate the gain means in that matrix. The electrical modulation source 108, by directly supplying the data to a particular gain medium, directly modulates those gain medium with laser emission capability. For example, modulation source 108 may directly modulate first laser-capable gain medium 116. The data signal is amplified by the first laser-capable gain means 116 in a band of wavelengths around approximately one or more of its cavity modes. The first gain means with laser emission capability 116 routes the modulated signal to a first input 120 of the multiplexer / demultiplexer 112.

Multiplexer / demultiplexer 112 routes the modulated signal to wavelength reflector 106. Wavelength reflector 106 routes a portion of the modulated signal as regenerative feedback back through multiplexer / demultiplexer 112 to the first gain medium with laser emission capacity 116 that supplied the modulated signal. The modulated signal and the reflected part of the modulated signal reinforce each other, in phase, at a resonance frequency of the first gain medium with laser emission capability 116. The modulated signal and the reflected part of the modulated signal are also amplified. by means of the first gain means with laser emission capacity 116.

The first gain means with laser emission capability 116 then transmits the reinforced modulated signal through the multiplexer / demultiplexer 112 and a portion of that reinforced modulated signal passes through the wavelength reflector 106 to the connection 110 to the output fiber. . Also, as described above, wavelength reflector 106 reflects a portion of that boosted modulated signal back, through multiplexer / demultiplexer 112, to the first gain medium. This regenerative narrow-band amplification occurs in each of the laser-capable gain means 102. Each of the laser-capable gain means 102 amplifies its own narrow band of discrete wavelengths.

The multiplexer / demultiplexer 112 acts as a narrow band filter to define the wavelength band developed by the first laser-capable gain medium 116. A natural characteristic of the multiplexer / demultiplexer 112 is to pass a band of wavelengths different in each of their outings. By

For example, the first output can pass the wavelength band from 1530 to 1531 nanometers (nm). The second output can pass the wavelength band from 1531 to 1532 nm. Therefore, multiplexer / demultiplexer 112 creates a narrow band of wavelengths fed back to each laser-capable gain medium 102. Consequently, each laser-capable gain medium 102 develops and amplifies a resonance wavelength within that wavelength band that corresponds to a cavity mode of the gain medium. When the amplified wavelength band is reinforced by the reflected modulated signal, then the gain means generates an optical signal of sufficient power to transmit via the passive optical network to the subscriber location. The reflected modulated signal provides resonant feedback to the laser-capable gain medium.

The laser-capable gain media array 102, multiplexer / demultiplexer 112, optical amplifier 104, and broadband wavelength reflector 106 can be integrated into a single integrated unit. The integral unit can be a single substrate where all components are grown on that single substrate. Alternatively, the integral unit may be made of two or more physically bonded and dissimilar material substrates.

The integral unit may use optical couplings in addition to optical fibers 122 in the optical path of the integral unit, such as air, lens arrays, or others such as waveguides. Optical fibers typically require a minimal bend radius and have other disadvantages that do not allow them to be used in a small compact space. However, optical couplings other than fiber optics 122 such as air or lens arrays can be used in a very small physical space to allow communication of the optical signals from one optical component to the next optical component. Furthermore, in an integral unit where all of the laser emitting capable gain media 102 are grown on the same substrate, the physical space between the gain media can be much shorter and smaller in physical size than if each of the the laser emitting gain means 102 was fabricated as a discrete component and placed on a common platform.

The substrate can be composed of Indium Phosphide where both active devices, such as gain media with laser emission capacity, as well as optical amplifiers or modulators, can be integrated together with passive devices, such as waveguide and multiplexer / demultiplexer. . The substrate can also be composed of other materials such as erbium doped silicon.

The laser emitting gain media array 102 comprises reflective semiconductor optical amplifiers. In some arrangements to which the present invention refers, said array may contain a large number of lasers, such as thirty-two or sixty-four lasers, which act as gain media, however the gain medium array may be as small as about four laser sources that act as gain media with laser emitting capability. The laser can be a distributed feedback laser having its center of wavelength fixed by a Bragg grating or a Fabry Perot laser diode or similar laser grown on a single substrate. Each of the laser emitting capable gain means has its own resonance wavelength and can be shifted to operate above or below a laser emission threshold.

Reflector semiconductor optical amplifiers may be laser emitting capable gain media that has a highly reflective back facet, such as 90%, with a front facet surface that is at a non-normal angle / non-perpendicular angle to the optical waveguide of reflector semiconductor optical amplifier. The highly reflective back facet causes a greater number of injected wavelengths to be amplified and reflected out of the reflective semiconductor optical amplifier. The front facet waveguide at a non-normal angle reduces the reflection index of the front facet and allows a greater amount of gain to be provided by the reflective semiconductor optical amplifier before laser emission takes place in the optical amplifier reflector semiconductor at the injected wavelengths.

Optical amplifier 104 coupled to multiplexer / demultiplexer 112 can amplify the optical signal arriving from multiplexer / demultiplexer 112 to increase overall gain and compensate for any insertion loss. There is a connection 110 to an output fiber in the output optical path from multiplexer / demultiplexer 112 to a passive optical network. The passive optical network may have an optical splitter component such as a wave division multiplexer.

The gain media capable of laser emission can also be continuous wave sources modulated by a separate matrix of modulators rather than directly modulated. Each continuous wave modulator is connected to its own gain medium. The continuous wave modulator data modulates the continuous wave from the gain medium capable of laser emission. Multiplexer / demultiplexer 112 can be a waveguide array, Echelle grating, or other similar technique to combine multiple unique wavelengths into a single waveguide with low signal power loss.

Wavelength reflector 106 may also be located at the output of a planar light wave circuit.

IS 2 365 486 T3

100 to provide regenerative optical feedback to each gain medium capable of laser emission 102 to develop the resonant wavelength of that gain medium. Wavelength reflector 146 can be created by etching a vertical facet in the waveguide to create a change in refractive index or be a Bragg grating or perhaps a coating on the edge of the integral unit / interface substrate with the output optical fiber with a reflector material to reflect a portion of the optical signal back to the multiplexer / demultiplexer 112 or it can be a grating at the input of the optical fiber 114 connected to the circuit of planar wave 100.

The construction of the planar wavelength circuit 100 having a laser emitting capable gain media array resembles a distributed laser having an external cavity that can operate above or below the laser emission threshold to develop or reinforcing multiple wavelength bands each having different wavelength bands. Thus, the distributed laser construction can be defined from gain means capable of emitting a section of laser light through the multiplexer / demultiplexer 112 to the wavelength reflector 106 and back to the multiplexer / demultiplexer 112 for each section of half profit. Each laser in the gain medium section may or may not have a reflecting front facet.

Figure 2 illustrates a block diagram of one embodiment of an array of four or more feedback lasers distributed in an integral unit. Coupled each array of four or more distributed feedback lasers 202 to a power splitter 212. Each feedback laser distributed in matrix 202 supplies a separate optical signal containing a different wavelength band than the other feedback lasers distributed in that matrix to the power splitter. Each distributed feedback laser in array 202 has its center wavelength of that wavelength band set by a Bragg grating at the output of the distributed feedback laser. For example, the first distributed feedback laser 216 has the center wavelength of the band of wavelengths supplied from the laser set by the first Bragg grating 224 intermixed with the gain medium of the first distributed feedback laser 216. A semiconductor optical amplifier 204 may be found in an output optical path of the power splitter 212 to compensate for insertion losses caused by the power splitter 212. There is a connection 210 for an output fiber to route the splitter optical signal of power 212 or at least in the output optical path of the power divider 212 to a passive optical network multiplexed by wave division. The distributed feedback laser array 202 can be integrated into a first substrate 226. The semiconductor optical amplifier 204, power splitter 212, and connection 210 can be integrated into a second substrate 228 that is attached to the first substrate 226 and which communicates the optical signals in the optical path between the first substrate and the second substrate using optical couplings 222 such as air or lens arrays but not without the use of optical fibers.

Thus, the active components can be manufactured on a first substrate 226 and the passive components can be manufactured on a second substrate 228 that are fused and physically bonded into an integral unit. The first substrate 226 as described can be a substrate of silicon dioxide, indium phosphide, or the like. Note, that Distributed Bragg Reflector lasers, for example, can also be used to generate the optical signal containing the wavelength band instead of distributed feedback lasers. Distributed Bragg Reflector lasers may have a Bragg grating at the laser output to establish the central wavelength of that laser.

Figure 3 illustrates a block diagram of one embodiment of a laser array and a broadband light source for providing an optical signal to each of the lasers contained in an integral unit. The integral unit may contain an array of four or more lasers such as Fabry-Perot laser diodes 302 on a first substrate 326. The integral unit may contain a second substrate 328 that contains a multiplexer / demultiplexer 312, a broadband light source 330, and a connection 310.

The broadband light source 330 supplies an optical signal containing a broad band of wavelengths, such as the C-band (1530nm - 1560nm), through an optical coupler 331 to the multiplexer / demultiplexer 312. Each of the Fabry-Perot laser diodes in matrix 302 is coupled to its own port on multiplexer / demultiplexer 312. Each of the Fabry-Perot laser diodes in array 302 receives a spectral portion of the optical signal from the broadband light source 330 so that the wavelength blocks a wavelength output from the Fabry laser diode- Perot within the bandwidth of the injected spectral portion. For example, the first Fabry-Perot 316 laser diode can receive a spectral portion of 1530 to 1531 nm. Fabry-Perot's first laser diode 316 can then reflect and amplify the spectral portion back through multiplexer / demultiplexer 312 to connection 310. Connection 310 is coupled to output fiber 314 to route an optical signal to the network. passive wavelength division multiplexing optics.

All Fabry-Perot laser diodes in matrix 302, multiplexer / demultiplexer 312, connection 310 and broadband light source 330 are integrated into one compact integral unit. The broadband light source 330 may consist of two or more super-luminescent diodes connected to provide orthogonal polarized signals, an erbium fiber acting as a broadband light source, an erbium-doped waveguide, a single diode super-luminescent units connected to the integral unit with polarization-maintaining fiber, a single super-luminescent diode on a chip, or other similar source that emits light. All the

ES 2 365 486 T3 components can be located in a single planar light wave circuit.

Figure 4 illustrates a block diagram of an embodiment of an array of four or more optical receivers and a multiplexer / demultiplexer integrated into a single integral unit. The integral unit may contain an array of four or more optical receivers 432, such as from a first optical receiver 434 to an N-th optical receiver 436, an electrical processing chip 438 for processing received data signals from λ1 to λπ, a multiplexer / demultiplexer 430 and a connection 410 for receiving an output fiber from a passive optical network multiplexed by wavelength division having a component for combining multiple optical signals from subscribers of that passive optical network. Each of the optical receivers in array 432 may contain one or more photodectectors.

The integral unit containing the receivers 440 can be located at the central office where it is necessary to process the return signals locally. Note that the integral unit of the optical gain means with laser emission capability can also be located in the central office where minimizing the space occupied by the components is of importance and all the components can be compactly placed, centrally. The first substrate 426 having the optical receptor matrix 432 may be composed of indium phosphide, gallium arsenide, silica, or other similar semiconductor substrates. The first substrate 426 can be connected in a planar wavelength circuit to the multiplexer / demultiplexer 430 on the second substrate 428. The electrical processing chip 438 that contains the electrical processing components that process the signal from the optical receivers in the array 432 may also be on another third substrate 442 made of silicon. The third substrate 442 can be physically connected and attached to the first substrate 426. The substrates 426, 428 in the integral unit can communicate the optical signals by waveguide without optical fibers, such as the first non-fiber-optic waveguide 422, the second non-fiber-optic waveguide 423, and the third non-fiber optic waveguide. non-fiber optic waves 425. All substrates 426, 428, 442 can be manufactured as a single integral unit 440.

Figure 5 illustrates a block diagram of one embodiment of an optical gain media array with laser emission capability and an array of optical receivers contained in an integral unit. The laser emitting capable optical gain media array 550 can generate N number of individual wavelength bands. Each optical gain medium with laser emission capability communicates an optical signal through the passive optical network to a corresponding subscriber, such as the subscriber's first location 552. The array of optical receivers 554 can receive N number of bands of individual wavelengths from those subscribers. For example, a first receiver may receive an optical signal generated from the subscriber's first location 552. Optical receiver array 554 may include the same number of receivers as laser-capable gain media in the laser-capable gain media array. For example, a first array of optical receivers 554 may contain thirty-two receivers and a first array of gain media capable of laser emission. The laser-capable optical gain media array 660 and the optical receiver array 554 may be on a single substrate or may be on separate substrates bonded together in the integral unit 556.

Each of the matrices 550, 554 can contain a multiplexer / demultiplexer or a power splitter to distribute the signals coming from and going to the passive optical network 558. In each of the matrices 550, 554, the components can be made grow on that substrate to make the spacing between individual components as small as possible. The integral unit 556 may also contain a band splitter filter 560 and a broad band light source.

The broadband light source supplies an optical signal containing a broadband of wavelengths, such as the L-band, to the multiplexer / demultiplexer in the optical gain media array 550. As described above, the multiplexer / demultiplexer routes narrowband optical signals to each of the optical gain means in array 550 so that the wavelength blocks the wavelength output of the capable optical gain means. of laser emission within the bandwidth of the injected spectral portion.

The laser emission capable optical gain media array 550 through its multiplexer / demultiplexer can send a single optical signal consisting of, for example, thirty-two individual wavelength bands contained within the C-band through from passive optical network 558 to a remote multiplexer / demultiplexer 564. Remote multiplexer / demultiplexer 546 may distribute the individual wavelength band from each laser-capable optical gain medium in matrix 550 to a corresponding subscriber location. For example, the remote multiplexer / demultiplexer 564 may distribute the wavelength band from the second laser-capable optical gain medium to the location of a second subscriber 566. The remote multiplexer / demultiplexer 564 can distribute all N individual wavelength bands from the laser-capable optical gain media array 550 in this way to corresponding subscriber locations.

The user / subscriber group can also transmit optical signals back to receiver array 554 at the central office in the L-band (1570nm - 1600nm). 560 band splitter filter separates wavelengths

ES 2 365 486 T3 of the L-band of the C-band lengths. The 560 band splitter filter routes the L-band signals to the matrix of the 554 optical receivers and the wavelengths of the C-band from the source. wide light to optical gain media array with 550 laser emitting capability.

The transmitters at the central office may use a first band such as the L-band to communicate information to the subscribers and the transmitters at the subscribers use another band such as the C-band to communicate information to the central office. Consequently, laser-capable optical gain media can generate individual optical signals in different wavelength bands such as O-band (around 1300nm), S-band (around 1480nm), etc.

A second multiplexer / demultiplexer in optical receiver array 554 routes individual C-band signals to each of the corresponding optical receivers. Each of the optical receivers receives a separate signal containing a different wavelength band than the other optical receivers in array 554. The laser emitting optical gain media array 550 and the optical receiver array 554 can be positioned at set angles such as approximately 90 degrees and approximately 180 degrees relative to the band splitter filter 560 to route optical signals with the waveguides, lenses or in air and without using optical fibers.

Figure 6 illustrates a block diagram of one embodiment of a laser array and an optical receiver array in one integral unit. The laser array 650 and receiver array 664 can each be coupled to a lens array 670, 672. The integral unit 676 may contain the laser array 650, a band splitter filter 660, a multiplexer / demultiplexer 674, the optical receiver array 664, a first lens array 650, a second lens array 672, and a connection 610 for a passive optical network. The multiplexer / demultiplexer 674 routes signals to and from the receiver array 664 and the laser array 650. The multiplexer / demultiplexer 674 routes signals to and from the passive optical network. The passive receiver array 664 is positioned close to the multiplexer / demultiplexer 674 so that the angle of the C-band wavelengths reflected from the band splitter filter 660 stays at a small angle. The optical receiver array 664 can be positioned at set angles such as 45 degrees or less to route the optical signals over the air and the second lens array 672. The 660 band splitter filter coated with a conventional dielectric coating can spread different wavelengths, bands such as C-band wavelengths and L-band wavelengths.

Fabrication of the array of optical receivers and lasers in a single integral unit can be accomplished in a simpler way by using a band splitter filter that reflects optical signals to the arrays at a small angle. If the laser array is operated in the O-band, approximately 1300 nanometers, rather than the L-band, then the reflected angle can be approximately 90 ° which can make compacting easier using a cast-iron prism. you do. All the configurations described above can be integrated into a passive optical network. The passive optical array may or may not block the wavelength of the laser-capable gain media by injecting narrow-band Amplified Spontaneous Emission light into the laser diodes that act as the laser-capable gain media.

In the foregoing specification, the invention has been described with reference to specific example embodiments thereof. However, it will be apparent that various modifications and changes can be made therein without departing from the broader scope of the invention as set forth fourth in the appended claims. The specification and drawings are therefore to be considered in an illustrative and not restrictive sense.