Abstract: A code multiplexing transmitting apparatus spread-spectrum modulates transmission data of a plurality of channels by spreading codes that differ from one another, combines the spread-spectrum signals of each of the channels and transmits the resultant spread-spectrum modulated signal. A spread-spectrum modulating unit for each channel includes a phase shifter for shifting, by a predetermined angle channel by channel, the phase of a position vector of the spread-spectrum modulated signal of each channel. As the result of such phase control, the phases of pilot signal portions of the spread-spectrum modulated signals of the respective channels are shifted relative to one another so that the peak values of the code-multiplexed signal can be suppressed.

Abstract: A system is provided for enabling a plurality of wireless communication transceivers to communicate. The system includes at least three wireless communication transceivers operable to communicate using a time division multiple access (TDMA) protocol. The at least three wireless communication transceivers are operable to alternatively serve as a master device according to a predetermined scheme to establish time slots for each of the transceivers, thereby enabling the at least three wireless communication transceivers to communicate in a conference-like manner and without a base station.

Abstract: A system, method, and apparatus for transmitting packet data over a wireless network to a mobile station is presented herein. Packet data are received at a wireless content switch which is interposed between a wireline network and the mobile station. The wireless content switch is equipped to detect lost packets, lost acknowledgments, and take appropriate remedial action, without invoking the congestion control and avoidance mechanisms of the transmission control protocol.

Abstract: A communications adapter system having a server, a pair of redundant I/O boards, a pair of redundant network interface cards and a pair of redundant switches. A software program monitors the system for failures, and is typically stored in the memory of the server. The system is fully redundant and can check connectivity from the server to a remote network device. The system can also run on FDDI systems.

Abstract: A method (FIG. 5) and apparatus (FIG. 3) to provide control and policy enforcement of WAP (Wireless Application Protocol) services in a wireless data networks is taught herein. WAP traffic is inspected with efficient algorithms to intercept un-registered WAP access and intercept dynamic change of user service selection. The intercepted WAP requests are modified with value-added parameters (such as QoS and subscriber identifiers) as per user and service provider agreement and table data. A series of strategies are described to blend wireless intelligence, user preference and service subscription, network operator requirements and service provider or enterprise preferences into routing and drive page generation. The means to dynamically provision users' service choices to wireless network elements are also presented without having to break the session within the system.

Abstract: Methods and apparatus which allow a wireless terminal (302) to simultaneously maintain connections with multiple base stations (304, 306) are described. Each wireless terminal (302) is capable of supporting multiple separate timing and/or other control loops one, for each base station connection thereby allowing the connections to operate independently and in parallel. Different control signals and/or data are transmitted on each connection that is established with a base station (302, 306). In this manner base stations (302, 306) receive different data allowing for asynchronous data transmission. The data received by the base stations (302, 306) can be supplied to a wired asynchronous network (308) without the need to combine the received data prior to supplying it to the wired network (308). The communications techniques of the invention can be used to implement soft handoffs without the need to duplicate data transmissions to multiple base stations.

Abstract: A method of and system for determining an ability of a first device to use an optical trail to communicate across an optical transport network with one or more other devices. The first device and the one or more other devices are external to the optical transport network. A first signal is transmitted from the first device, where the first signal indicates that at least a first port of the first device is available to be an endpoint for an optical trail across the optical transport network. The first signal is received at a first transport network device of the optical transport network. A second signal is transmitted from the first transport network device, where the second signal identifies a second port of a second transport network device included in the optical transport network to which the first device can send signals corresponding to an optical trail. The second signal is received at the first device.

Abstract: A method for providing an animated audio message includes wirelessly receiving indicia of an audio message and an image, and animating the image in association with the audio message to produce an animated audio message. A system for providing animated audio messages includes a wireless interface that can receive wireless communications that provide or identify an audio message and provide or identify an image. An animator is coupled to the wireless interface and can animate the image in accordance with the audio message to form an animated audio message. An animation interface is coupled to the animator and can transfer the animated audio message from the animator toward a desired destination.

Abstract: A proxy at the interface between a wireless communications system and a packet network intercepts all traffic between the wireless communications systems and the packet network and re-formats the intercepted traffic according to an optimal maximum transmission unit size between the interception point and the final destination, excluding the wireless link from computation of the optimal maximum transmission unit size. Typically this will result in packets from the wireless communications system being aggregated into a larger maximum transmission unit size, while packets from the packet network are fragmented into a smaller maximum transmission unit size. Congestion at intermediate nodes within the packet network is reduced, while end-to-end bandwidth utilization and latency at the final destination are improved.

Abstract: A service provider providing gatekeeper backup services to a plurality of off-site voice packet networks from a single central backup gatekeeper. The gatekeeper maintains a database of local gatekeepers for which the backup service is to be provided. The services provided may be identical to those provided by the corresponding local gatekeeper, or may be a more basic level of service to reduce the cost of the backup service.

Abstract: The invention relates to a method for transferring a call between a telecommunications network and a data network. Between the data network and the telecommunications network an internetwork computer (gateway) is arranged, by which voice data of the call is converted from a format used in the telecommunications network into a format used in the data network, and conversely. Signaling data of the call is processed by a data processing device arranged in the data network. In order to make full use of the available functions of a signaling channel in telecommunications networks, even with voice connections that are partially over a data network, it is proposed that the signaling data be transferred bit-transparently between the gateway and the data processing device.

Abstract: A system and method for dynamically determining a route through one or more switch devices at program execution time. A program operable to perform a programmatic request to dynamically determine a route may be created. For example, the request may specify a first endpoint (e.g., channel) of a first switch device and a second endpoint (e.g., channel) of a second switch device. In response to the request, the system may dynamically determine a route from the first endpoint to the second endpoint during execution of the program. Information indicating the determined route may be returned to the program.

Abstract: One embodiment of the present invention comprises a system and method for graphically defining a route through one or more switch devices. the user may interact at a high level with a graphical user interface of a visual route editor to graphically create the route. For example, the visual route editor may display icons, diagrams, or other information that visually represents the route, e.g., by displaying information graphically representing the path that the route takes through the one or more switch devices.

Abstract: The call data and hardware cache for a dial-up access concentrators caches the hardware device setup and the communication connection data created for a call connection for use in the next successively received incoming call. The call data and hardware cache for dial-up access concentrators enables the existing physical hardware connection that comprises the call connection in the dial-up access concentrator, the call processing and call connection resources to remain available for use in the next successively received incoming call. This step also retains the communication connection data comprising the call setup and call management data in the shelf controller and the call processing data in the call signal processor card for possible reuse.

Abstract: A method and apparatus for migrating one or more users from a source server module to a destination server module in a manner avoiding information discontinuities or otherwise degrading the users' viewing experience.

Abstract: The present invention relates to a local retransmission scheme, which uses Transport Control Protocol (TCP) in an unreliable network. It provides reliable transmission for out-of-order TCP data packet in an unreliable link. It recovers non-congestion loss packets. It avoids incorrect adjustment of window size in TCP source end. It applies TCP local retransmission scheme, which checks together a link layer transfer sequence and a TCP source delivery sequence. With inserting timestamp of local sequence number, which is in TCP data packet and TCP acknowledgement packet, together with acknowledgement number AN, it is defined whether a data packet is lost and retransmitted. Then, with explicit retransmission ERN feedback, a TCP source false action is avoided. Therefore TCP performance of a wireless network is greatly improved.

Abstract: A method capable of optical packet switching even in a case where physical optical data in an optical packet switch has not the shape of a packet but the shape of continuous data, and a system therefore are provided. The optical switching method includes the steps of (a) detecting input terminals into which an optical packet is input, of an optical switch and switching the optical packet to destination output terminals of the optical packet, and (b) when there are the input terminals into which the optical packet is not inputted in step (a), detecting other input terminals into which the optical packet, which direct an output terminal among the plurality of output terminals connected to the input terminals, is inputted, and searching a blank output terminal and switching dummy data from the input terminal to the blank output terminal.

Abstract: A method of allocating switch requests within a packet switch, the method comprising the steps of establishing switch request data at each input port; processing the switch request data for each input port to generate request data for each input port-output port pairing; comparing the number of requests from each input port and to each output port with the maximum request capacity of each input port and each output port; allocating all requests for those input-output pairs where the total number of requests is less than or equal to the maximum request capacity of each input port and each output port; reducing the number of requests for those input-output pairs where the total number of requests is greater than the maximum request capacity of each input port and each output port such that the number of requests is less than or equal to the maximum request capacity of each input port and each output port; and allocating the remaining requests.

Abstract: A method of transmitting data from a sender to a number of recipients in a system with a multilayer protocol architecture, in which the data are divided for organizational purposes into data packets having header data and payload data, a transmitting and/or receiving unit and a communication system. The transmission of data in the form of a point-to-multipoint transmission over a general channel, in particular in a mobile radio system, is carried out by adding to packet data which are being sent to multicast groups control data for the identification of a specific multicast group.

Abstract: A broadcast satellite network transmits from a source to multiple router nodes digital real-time program information and best-effort data. The router nodes are specifically suited for extracting best-effort data streams from the multiplexed signal received via, e.g., a satellite. A number of management techniques are disclosed. According to one technique, a packet is formed having a network layer header, including a destination address for routing a packet to a destination, a second header identifying a syntax and semantic by which a payload of the packet may be parsed in a predefined fashion, and a payload containing a command to be executed by each of one or more to-be-managed nodes to which the packet is destined. The packet is transmitted a plural amount of times to a plurality of nodes, including the one or more to-be-managed nodes, but the command in the particular packet is executed only a single time. According to other techniques, the nodes are divided into groups.

Abstract: A broadcast satellite network transmits from a source to multiple router nodes digital real-time program information and best-effort data. The router nodes are specifically suited for extracting best-effort data streams from the multiplexed signal received via, e.g., a satellite. A number of management techniques are disclosed. According to one technique, a packet is formed having a network layer header, including a destination address for routing a packet to a destination, a second header identifying a syntax and semantic by which a payload of the packet may be parsed in a predefined fashion, and a payload containing a command to be executed by each of one or more to-be-managed nodes to which the packet is destined. The packet is transmitted a plural amount of times to a plurality of nodes, including the one or more to-be-managed nodes, but the command in the particular packet is executed only a single time. According to other techniques, the nodes are divided into groups.

Abstract: A data switching system comprising one or more I/O elements each comprising a plurality of first input/output ports adapted to receive and transmit data packets or cells to and from an external data network, and one or more second input/output ports adapted to receive and transmit data packets or cells, means for providing first routing information relating to at least one packet or cell to be output from one or more of the second port(s), each I/O element being adapted to transfer data packets or cells between the first ports and the second port(s) and to output data packets or cells comprising corresponding first routing information from the second port(s), a switching element having a plurality of third input/output ports being adapted to receive and transmit data packets or cells, the switching element comprising means for receiving on a third port a data packet or cell as well as the corresponding first routing information, determining, on the basis of the first routing information, port information indi

Abstract: Arbitration for a switch fabric (e.g., an input-buffered switch fabric) is performed. The switch fabric has a set of ports. Each port from the set of ports is associated with its own set of links. The set of ports includes a first port and a second port. A link is selected from the set of links associated with the first port based on a weight value associated with each remaining link associated with a candidate packet and being from the set of links associated with the first port. A first penalty for a weight vector entity associated with the first port is determined by based on a weight value associated with each link from a first subset of links from the set of links for the first port. Each link from the first subset of links is not associated with a candidate packet.

Abstract: A multi-module switching system comprising at least two switching modules adapted for receiving data packets from at least one input adapter and transmitting the data packets to at least one output adapter, each of the switching modules including a shared buffer for buffering a portion of a data packet received from an input adapter and transmitting the portion to an output adapter. One of the switching modules is a master module receiving a portion of a data packet containing a packet header and sending control information contained therein serially to each other switching module as a slave module.

Abstract: A method is provided for a dynamic optimization of network resource allocation on the part of a network service provider. In particular, the method of the invention provides an analytical framework for a determination by network service providers of an optimal resource allocation among links in a service provider's own network and links obtained from other network service providers. The analytical framework of the invention also incorporates, as a parameter, the provision of link capacity to other network service providers in the determination of an optimal resource allocation. In a preferred embodiment of the invention, such an optimal resource allocation is determined in respect to revenue maximization for the network service provider.

Abstract: A programmable network device is described. The programmable network device executes software modules resident on its hardware to support assorted applications and network management services. These modules may be dynamically loaded, unloaded, or modified without interrupting network traffic routed through the device. The loading and unloading of modules can be administered remotely, via a network backbone, service provider network, LAN, or other internetwork coupled to the device. Alternatively, administrators may alter the operating parameters of individual management modules via the network to effect performance gains or modify existing operating parameters.

Abstract: A method and an arrangement for controlling data packets in a computer network forwards particular data packets, from the whole of a data stream, via a gateway with a host processor. The particular data packets are forwarded to subsystems for further processing, and data packets are introduced into the data stream by the subsystems via the gateway. In this context, a data packet router forwards the data packets directly, i.e. past the host processor, to the subsystems, and the data packet router introduces the data packets coming from the subsystems directly into the data stream using an interface device .

Abstract: A head of line (HOL) blocking count value, which is directly proportional to the committed traffic load for traffic flow through an output port within a multi-stage switch mesh, is computed for a path by adding the values associated with all output ports within the path. In selecting a route, all paths from the source to the destination are identified and sorted by head of line blocking count value. Rather than selecting a path based on traffic load, the path having the lowest head of line blocking count value and sufficient capacity for the requested traffic is selected, with selection between paths having equal head of line blocking count values being made based on traffic load.

Abstract: An apparatus and method for virtualizing a queue pair space to minimize time-wait impacts. The apparatus and method allocate virtual queue pairs from a virtual queue pair pool of a node to connections between the node and other nodes. The connection is established between a physical queue pair of the node and physical queue pairs of other nodes. However, from the viewpoint of the other nodes, they are communicating with the present node using the virtual queue pair and not the physical queue pair for the present node. By using the virtual queue pairs, the same physical queue pair may accommodate multiple connections with other nodes simultaneously. Moreover, by using a virtual queue pair rather than a physical queue pair, when a connection is torn down, the virtual queue pair is placed in a time-wait state rather than the physical queue pair. As a result, the physical queue pair may continue to function while the virtual queue pair is in the time-wait state.

Abstract: A system and method for increasing bandwidth usage between an access point and a wireless device are described. One embodiment can include an access point, a prioritizer, and a priority storage device. These components can increase bandwidth usage between an access point and a wireless device by allocating previously unused transmission slots.

Abstract: A Local Area Network based on a parallel bus architecture is disclosed. The LAN provides a means of utilizing relatively low cost CMOS circuitry to obtain performance superior to LAN's utilizing more exotic high speed technology. The disclosed LAN is based on a parallel bus having n×8 data lines, ±power lines, and a clock line. The bandwidth of the LAN is the product of the number of data lines times the clock speed. Bandwidth is therefore scalable by increasing either the clock speed, the number of data lines, or both. Access to the bus is provided via ports which include transceivers, a clock receiver, and a configurable hardware interface. Each port is assigned an address based on a data line and a clock cycle. The invention features a network that becomes more efficient as usage increases, ports that can accept any medium, and an architecture that facilitates implementation of a true “STAR” LAN configuration which interfaces between two or more serial communications links.

Abstract: A method of bandwidth management enabling to insure a guaranteed bandwidth to each station of transmission network comprising a plurality of stations (10, 12, 14) forming a logical ring wherein a token frame is circulating from station to station, each station being allowed to transmit a credit (c) of data bytes upon reception of the token frame wherein the credit is increased in proportion to a variable TRTT standing for Token Round Trip Time which is the time taken for the token frame to circulate around the logical ring since the preceding reception of the token frame by the station. The credit is increased in proportion of a variable CIR standing for Committed Information Rate which is the guaranteed transmission rate that the station can use to transmit data wherein the value of CIR is determined by a class of bandwidth which has been previously selected by the station upon the preceding reception of the token frame by the station.

Abstract: A system and method for improving the ability of a wireless communications network, such as a packet-switched data communications network, to provide service to mobile user terminals. The system and method employs a mobile access point, adapted for use with the packet-switched communications network, to provide a mobile wireless user terminal with access to the network, and a method for using the same. The mobile access point can be mounted to a mobile vehicle and receives substantially constant power from the vehicle, and is adapted to transmit and receive communications signals to and from wireless user terminals, fixed access points and other networks and mobile access points. The mobile access point includes at least one or more transceivers, which allows the access point to support multiple wireless communication protocols. A first protocol may be supported allowing network access, and a second protocol may be used for backhaul service.

Abstract: The present invention relates to an arrangement and method for providing wireless data communication services, between a client station (10) and a service providing station (15) and/or a computer network (13, 33), each of the client station (12), service providing station (15) or the computer network (13, 33) being connected to at least one radio transceiver (11, 12) and each being arranged with means (20, 30, 31) to convert data to be transmitted to data packets or data packets to data. The radio transceiver (11, 12) is arranged to transmit and/or receive data packets with at least one predetermined, by a user determined or randomly selected low radio frequency, said low radio frequency being within a range of about 1 kHz to about 30 MHz, preferably one or several of: 100-1800 kHz, 1810-1850 kHz, 3500-3800 kHz, 7000-7100 kHz, 10100-10150 kHz, 14000-14350 kHz, 18068-18168 kHz, 21000-21450 kHz, 24890-24990 kHz and 28000-29700 kHz bands.

Abstract: A packet switched network is comprised of a communications network, such as the existing IP network, and a number of distributed protocol converters connected to the IP network. X.25 user data terminals are connected to the protocol converters. Each protocol converter serves as an interface between the user data terminals and the IP network by performing protocol conversion between TCP/IP protocol and X.25 protocol.

Abstract: Method for segmented message transmission wherein each message is first divided into segments and the segments are fragmented. A segment parameter is applied to each segment, and a segment identifier to each fragment. The fragments are provided to a lower level for preparation into frames for transmission. One embodiment is applied to the transmission of short duration messages, such as control messages.

Abstract: Apparatus, and an associated method, for providing a radio link layer control procedure to maintain the sensitivity of UDP-Lite-formatted data at an RLP (Radio Link Protocol), or other, layer. An indicator generator generates an indication of the sensitivity-type of data that is formatted at the RLP layer. An RLP packet is generated, including the sensitivity data indicator value, and sent to a receiving station. When received thereat, the value of the sensitivity data indicator is utilized and subsequent actions, whether to permit retransmission of the data in the event of erroneous-, or non-, delivery is made.

Abstract: A method and system are disclosed for enabling full-service communications between a full-service cable modem termination system (fsCMTS) and a plurality of full-service cable modems (fsCM's) for a conventional two-way hybrid fiber-coax (HFC) cable television network. Full-service communications include data, voice and video. Video includes broadcast quality MPEG-2 transport packet streams and Internet protocol media streams. A multi-channel full-service media-access-control (fsMAC) coordinates the access to the shared upstream and downstream channels. At lease two downstream channels and at least two upstream channels are provided. Several MAC management messages are defined to enable multi-channel full-service MAC domain to be defined and to enable packet-by-packet true seamless channel change. Multiple upstream channels can be used in various ways to best optimize the use of the spectrum for meeting the quality-of-services needed by different services.

Abstract: Hardware and resource usage penalties associated with the conventional remote device management approach of occupying a robbed DS0 channel for only one management session at a time are obviated by programming a multi-digital circuit servicing host site-resident integrated access device to provide for effective simultaneous management of multiple remote digital communication devices by one or more workstations. Although only a single robbed in-band (T1) channel per remote site is used, it is unnecessary to terminate each high speed digital (T1) link with an associated T1 Service Unit and ISDN Service Unit pair at the central office site.

Abstract: To synchronize a communication system via a packet-oriented data network, a frequency offset of a time-measuring device is determined by a measuring device using only data packets with approximately the same forward and return times.

Abstract: An integrated communication system for communicating Ethernet and PDH/SDH/SONET data using time division multiplexing techniques is provided. The integrated communication system time division multiplexes PDH/SDH/SONET data with Ethernet data, and transmits and receives the combined data stream using Ethernet-based communication technology. The integrated communication system is cost effective for providing both Ethernet and PDH/SDH/SONET communication services, since separate transmission facilities are not required. In addition, the time division multiplexing method is more cost effective than the wave division multiplexing (WDM) method since WDM equipment is not required. The integrated communication system can act as a standalone system or be incorporated into other network systems.

Abstract: A wavelength-dependent variable mirror suitable for application in tunable semiconductor lasers is disclosed. The variable mirror comprises a coupler having two input ports and two output ports operable to distribute a known level of light coupled into a first input port, optical channels extending from each of the two coupler output ports of and a wavelength-selective device connected to each of the extended optical channels. In one aspect, the wavelength selective device connects the two extended channels forming an optical loop, which reflects a known level of light back to the coupler input ports. In another aspect, the wavelength selective device reflects a known level of light at a predetermined wavelength back to each of the extended channels to an input port of said coupler. In yet another aspect, a phase controlling element is introduced in at least one optical channel, which introduces a known amount of phase change in the light sent back to the coupler.

Abstract: The present invention has applications in the field of color displays, including computer monitors, video games, television, and other applications that may require a variety of light wavelengths. In one aspect of the invention, a light generator can generate light having selected proportions of red, green, and blue wavelengths from a single source of blue light. In a specific embodiment, the light generator includes a blue laser for generating a first beam of blue light. In another aspect of the invention, beamsplitters are used to split the beam of blue light into separate beams to generate light having a single color in each beam. In one such embodiment, upconversion lasers are used to generate each of the single colors.

Abstract: Harmonic lasers are provided. A third harmonic laser includes a first high reflector and an output coupler forming a resonator cavity having an optical axis. The resonator cavity includes a laser medium for producing a fundamental beam. Desirably, the laser medium is Nd:YAG, Nd:YLF, Nd:YV04, although other laser mediums are also contemplated such as Ti:sapphire, Nd:YAB and the like. The laser medium can be pumped by any desired source for example laser, laser diode, laser diode bar, fiber coupled laser diode bar or lamp which are well known in the art. The laser medium can be either end pumped or side pumped which are also well known. The first high reflector is reflective of a fundamental beam. A second harmonic generator is located within the cavity formed between the first high reflector and the output coupler for generating a second harmonic beam from the fundamental beam. The output coupler is highly transmissive for second harmonic beam and partially transmissive for a fundamental beam.

Abstract: An external cavity laser system comprises a reflective optical amplifier 3, an input waveguide 4 for receiving an optical input signal from the reflective optical amplifier 3, a Bragg grating 5 for reflecting a portion of the optical input signal back along the input waveguide 4 to define a resonant cavity with the optical amplifier, and a reflection photodiode 30 for detecting the signal portion reflected by the grating 5 and for supplying an electrical feedback signal indicative of the signal portion. A transmission photodiode 6 is also provided for detecting the signal portion transmitted by the grating 5 and for supplying an electrical feedback signal indicative of that signal portion. These feedback signals are supplied to a control circuit which controls a phase modulator to modulate the phase of the optical input signal so as to ensure zero detuning between the dominant signal mode and the peak of the grating.

Abstract: A structure for holding an optical subassembly such as a laser and which minimizes the tilt of the optical subassembly. Pads are placed between the optical subassembly and the housing forming grooves along the inside of the housing and between the pads. The solder for mounting the subassembly to the housing is placed in the grooves. The volume of the solder is chosen so that it does not overflow the grooves. But the solder can be constructed so that its height is greater than the height of the grooves. The optical subassembly is placed against the solder with a downward force and heat is applied to the bottom of the base to melt the solder.

Abstract: A laser driver circuit includes a biasing current source, a threshold current source, and a modulation current source, wherein the threshold current source produces a threshold current in response to an input signal with an interval exceeding an interval of a modulation current such that said interval of the threshold current includes the interval of said modulation current. The laser driver circuit drives the laser diode by a sum of a continuous bias current, the threshold current and the modulation current.

Abstract: A surface emitting semiconductor laser device has a pair of DBRs having opposite conductivity types, a pair of cladding layers having opposite conductivity types, an undoped active layer and a current confinement layer. The boundary between the p-type region and the n-type region of the laser device resides within the active layer, thereby reducing the operating voltage of the laser device.

Abstract: A method of simultaneously depositing dielectric layers on both facets of an optical device and devices made therefrom. The steps of the method are selecting a substrate; forming an optical device on the substrate; forming an active-layer pumping structure on the optical device; forming facets in the optical device with at least two different orientations; and coating a user-definable number of dielectric layers onto the facets. The dielectric layers may be deposited in single dielectric layers or in pairs of dielectric layers. Single layers are useful for forming optical amplifiers while dielectric pairs are useful for forming lasers.

Abstract: The present invention is directed a method of fabricating a VCSEL. First, a substrate with a back surface and a front surface is provided. Then, a first reflector, an active region, and a second reflector are disposed on the front surface. The first reflector is disposed on the front surface. The active region is interposed between the first reflector and the second reflector. Then, anti-reflection features are formed into the back surface of the substrate to reduce specular reflection of light into the active region.