RU2289207C1 - Interface for transferring discrete information through optical channel - Google Patents

Abstract

FIELD: systems for transferring discrete asynchronous information through fiber-optics or open optical channel; channel level of transfer system (sublevel of medium access control).

SUBSTANCE: transferred bits of information are converted into optical signals using the number of transferred bits of information. These signals are multiplexed in optical range by delays for defined time intervals and by changing wave-length, and grouped optical signal is forwarded to the transfer channel. On the receiving end of transfer channel the optical signal is demultiplexed, signal parts are delayed for defined time intervals and detect. Transferred bytes of information are put to output buffer register using synchronizing signal, which is transferred simultaneously with informational bits. Unlike known interfaces, the proposed interface does not have numerous coding and decoding, grouping of transferred messages into frames, etc. Due to these facts, useful information transfer speed is increased; noise immunity is improved, especially in impulse noise environment and outer mechanical and climate factors.

EFFECT: increased noise immunity in impulse noise environment.

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Description

The interface is a set of unified devices, communications and signals through which the communication of the source and receiver of information.

The invention is a method and device and relates to the field of information transmission systems, measuring equipment, telemetry and optoelectronics and can be used for transmission of discrete asynchronous information via an optical fiber cable or an open optical channel and relates to the channel level of the organization of the transmission system (access control sublevel to environment).

Known interfaces (methods and devices) for transmitting discrete (digital) information via optical channels, such as:

- according to ITU-T, G.703 protocol;

- Ethernet (IEEE 802.3);

- Fast Ethernet (IEEE 802.3u);

- Gigabit Ethernet (IEEE 802.3z);

- Fiber Channel (FC-PH);

- FDDI (IEEE 802.2);

- ATM (SONET), etc.

The essence of the interfaces is that information from various sources of information is digitized using analog-to-digital converters, combined by time multiplexers into one structured stream. Data from parallel code is converted to serial code. The resulting bit sequences are grouped into digital streams, which can have varying degrees of hierarchy, with digital streams of a higher degree of hierarchy combining streams of a lower degree of hierarchy. These digital streams at the transmitting end of the transmission line encode and frame to increase the noise immunity. Each frame (block) has service fields, data field, as well as fields of synchronization signals. At the physical level, frames are linearly encoded (with a two-level code) for transmission over the optical transmission channel and converted using optical transmitting modules into a sequence of optical pulses. At the receiving end of the transmission line, inverse transforms are performed.

For the G.703 protocol, the lowest degree of hierarchy for both American and European plesiochronous information transmission systems has the main digital channel (BCC) - this is a digital signal of zero level at a speed of 64 kbit / s (Digital Signal of level 0 or DS0). Higher hierarchy have digital streams of the first level DS1 (with a speed of 1544 kbit / s) for American systems and E1 (with a speed of 2048 kbit / s) for European systems, streams of levels 2, 3, 4, 5 (DS2, DS3, DS4 , DS5 or E2, E3, E4, E5).

For synchronous transmission systems (SDH) with an ATM, SONET, etc. interface, the lowest hierarchy level is STM-0 (Synchronous Transport Module of level 0, corresponding to SONET OS-1). The higher hierarchy levels are streams STM-1, STM-2, and so on up to STM-256 (for SONET, respectively, STS-1, STS-2, and so on up to STS-768). Streams are divided into virtual containers (frames or tribes). In this case, the digital stream is encoded by one of the interface codes, usually a three-level HDB3 (High-Density Bipolar code of order 3) code. For optical channel transmission, linear recoding is performed, as a rule, two-level. Typically, optical transmission channels use the codes CMI, MCMI, mbnb, NRZ [1].

At the receiving end, inverse transforms occur.

The main disadvantages of the considered interfaces include:

- increased probability of loss of reliability of transmitted messages due to numerous code transformations;

- sophisticated equipment, including converters of parallel code to serial and vice versa, channel controllers, high-speed dual-port RAM, microcontrollers, electronic switch, and other complex nodes.

A device and method [2] are known that implement the interface according to the G.703 protocol according to ITU-T for transmitting discrete information.

The method consists in the fact that the main information flows of the DS0 level are multiplexed (combined) into the information flows of the DS1 level, which are once again multiplexed (combined into one stream), convert the HDB3 butt code into a linear code, modulate the optical radiation, direct this radiation into the optical channel communications, convert optical radiation at the receiving end of the transmission channel into electric current, amplify electrical signals, convert the linear code to the DS1 interface layer, demultiplex DS1 level signals into level signals Nya DS0.

The device contains electronic multiplexers of the main information flows of the DS0 level to the information stream of the DS1 level in HDB3 code; an electronic DS1 level stream multiplexer and an HDB3 butt-to-line code converter, an emitter matching unit with a code conversion device output, an optical signal emitter (laser or light emitting diode), an emitter optical output stabilization and temperature stabilization unit, a photo detector, a bias voltage source for a photodetector, a broadband amplifier of an electric signal emitted in the load of a photodetector, a linear code to DS1 code converter, a demultiple sors, converting the signals into signals DS0 DS1 level, optical connectors and optical cable.

The device operates as follows.

Information signals in parallel code are fed to the inputs of multiplexers, combining them into digital streams of the zero level of the DS0 hierarchy. DS0 streams by the first hierarchy level multiplexer are combined into DS1 type streams, which are combined by the second hierarchy level multiplexer into a single stream HDB3, which is input to the HDB3 line-code converter. The linear code is fed to the input of the emitter through a matching device. The emitter through optical connectors directs the optical information signal, which is a linear two-level code, to the fiber optic path (BOT). A photodetector is installed at the BOT output, connected to demultiplexers that convert the linear code to DS1 and DS0 codes.

The considered method and device have the following disadvantages:

- with each code conversion, the probability of the appearance of bits affected by errors increases;

- for the transmission of information requires sophisticated equipment, including multiplexers and demultiplexers of the DS0 and DS1 levels, and other complex nodes.

There is another method and device for transmitting discrete information through an optical communication channel [3, Fig. 1], which implement the ATM interface (SONET).

The method consists in converting parallel discrete data into a serial code, mixing clock pulses into this code, converting this code into linear, modulating the laser diode code, sending it to the optical transmission channel, detecting at the receiving end, amplifying and limiting the level converted to electrical signals, restore synchronization signals and discrete data, convert a sequence of bits into a parallel view of information.

The device comprises a photodiode, a transimpedance amplifier, a limiter amplifier, a synchronization and data recovery unit, a serial-parallel converter, a parallel-serial converter with a sync pulse synthesizer, a laser driver, a laser diode.

The device operates as follows.

The information prepared for transmission through the optical channel is transmitted in the form of a parallel code to a parallel-serial converter with an integrated sync pulse synthesizer, which converts the parallel code into serial and mixes the resulting digital stream with synchronization signals. The laser diode converts the electric digital stream into an optical signal and directs it to the optical transmission channel. A parallel-serial converter with an integrated clock synthesizer is made on a MAX3691 chip, and the laser driver is on a MAX3667 chip. The MAX3691 microcircuit contains a 4-bit parallel data register, a phase detector, a shift register, an output matching amplifier [4]. Conversion of a parallel code into a serial one is carried out using a shift register, into which information from the input register is transferred. The shift of information in the shift register is carried out by the signals from the output of the phase detector, which emits synchronization signals. The laser driver ensures the stability of the laser operating point, monitors the power of laser radiation. From the laser output, information enters the optical transmission channel.

A photodiode is installed at the output of the transmission channel, the output signals of which are amplified by a transimpedance amplifier, then by a limiter amplifier, and transmitted to a synchronization and data recovery circuit (SIDS). The amplifier-limiter with built-in SFSD is implemented in a chip type MAX 3675 [5]. From the output of MAX3675, synchronization and data signals are fed to the inputs of the MAX3681 chip.

The MAX3681 chip is a series-parallel converter [6]. The microcircuit contains two registers: a 4-bit shift register and a 4-bit parallel register. Data is fed to the input of the shift register, and from its outputs, according to the synchronization signals, they are written to the first port of the parallel register. From the outputs of the second port of the parallel register information is sent to the consumer.

The disadvantages of the device and method are:

- a complex synchronization system, even a small jitter (phase oscillation of the synchronization pulses) can lead to loss of information;

- unreliable schemes for converting parallel code to serial and vice versa, subject to the effects of impulse noise;

- conversion schemes cannot be used in telemetry devices of moving objects with a high level of electromagnetic interference from power units exposed to such external factors as temperature, humidity, pressure, shock, and vibration.

Another method and device is known that implements the ATM interface (SONET) of synchronous transmission systems (SDH) for transmitting discrete information over an optical channel, described in [7 and 8].

The method consists in generating optical pulses by synchronizing the laser with a standard SDH timer, amplifying optical pulses, branching them into N channels, modulating optical pulses in each channel with a linear SDH technology code, delaying optical pulses in transmission channels for a time T · N / I, where T - period of the pulse sequence, N - number of channels, I - channel number (I = 1 ÷ N), combining pulses into a single stream, amplifying a group signal, the direction of the stream to the information transfer channel, temporary demultiplexing optical signal and the allocation of the synchronization frequency.

The device contains a mode-locked laser, synchronized by a standard timer of SDH systems, directing optical pulses through an optical amplifier to an optical splitter with a 1X8 transmission matrix. The outputs of the splitter are connected to the inputs of the optical combiner with a transmission matrix 8X1 through series-connected optical modulators and optical delay lines, and the control inputs of the modulators are connected to the outputs of the reference timer of SDH systems. The output of the combiner is connected to the optical transmission channel through an optical amplifier, and a temporary demultiplexer synchronized by the synchronization device is installed at the output of the optical transmission channel.

The device operates as follows.

A mode-locked laser is synchronized from the reference timer of multiplexed SDH reference systems. A stream of optical pulses with a duration of τ and a repetition period T is fed through an optical amplifier to an optical splitter that spatially divides the light flux into eight equal parts, each of which is fed to optical modulators. From the output of each of the modulators, the radiation passes through the corresponding segments of optical fibers playing the role of an optical delay line. In this case, the delay time from the output of the 1st modulator is chosen very small, we will consider it equal to zero. After the output of the 2nd modulator, the optical pulses are delayed by 1/8 T, etc., and after the eighth modulator - by 7/8 T. From the output of all modulators, the flows are fed to the inputs of the adder, from the output of which the combined group stream after gain in the optical amplifier is fed into the transmission line (i.e., into the optical channel). To compensate for losses (if necessary), an intermediate optical amplifier can be used in the line. From the output of the line, the optical group signal is amplified by an amplifier and fed to an optical time demultiplexer, synchronized using a synchronization device. The device uses fully optical elements - a laser, optical splitters, modulators based on electro-optical crystals of LiNbO ₃ , optical amplifiers and optical delay lines.

The disadvantages of the method and device are related to the fact that synchronization signals are associated with encoding algorithms. Without coding, when transmitting a logical “0” group, synchronization will be lost due to the absence of optical pulses at the receiving end of the transmission line. In this regard, the inability to work in conditions of moving objects for transmitting telemetric information, since the system becomes sensitive to pulsed electromagnetic interference, jitter of the synchronization phase, the dependence of the delays in the electronic nodes of the synchronization circuits on changes in external temperature.

In addition, the need to mix synchronization signals into a structured digital stream, the need to equalize the transmitted units and zeros so as not to lose synchronization, leads to an increase in redundancy and, therefore, to a decrease in the transmission rate of useful information.

Numerous transcodes increase the cost of equipment, especially for high-speed transmission channels.

Closest to the technical solution to the proposed method and device is the method and device described in [9] and that implements PDH and SDH interfaces.

The method is as follows.

Information from M various sources (television cameras, microphones, sensors, etc.) by analog-to-digital converters is presented in parallel code. Using a digital switch and special encoders that perform noise-resistant coding, N-bit digital data from M sources in parallel code is converted into a bit sequence - a structured digital stream. This stream, using the temporary grouping unit, is divided into separate PDH blocks (frames / tribes) of the required hierarchy level, which are formed by the SDH multiplexing unit into STM-N modules (with a header, with sectional, multiplexed, path and interface coding). STM-N modules are linearly encoded and modulate the optical radiation source. If parallel transmission of several STM-N modules is necessary, the optical radiation is multiplexed along the wavelength using a wave optical multiplexer. A group optical signal is sent to a fiber optic transmission channel. At the output of the transmission channel, the optical signals are demultiplexed, photodetected, the physical sequence STM-N is converted into a logical pulse sequence, composite signals (tribes) of the required PDH level are extracted from it. The PDH group signals (tribes) are disassembled to the required level, the necessary time slots are allocated, the signals are decoded and restored in the original form, in the form of bytes of information in the parallel code.

The device contains M transmitting units connected to M receiving units through sequentially mounted optical combiner with a transmission matrix M X 1 (wave multiplexer), optical amplifiers, fiber-optic transmission channel, optical spectrally selective coupler with a transmission matrix 1 X M (wave demultiplexer )

Each of the M transmitting units contains a channel-forming unit, a temporary grouping unit, a level matching unit, an SDH multiplexer that converts a physical pulse sequence into an STM-N logical sequence, a linear coding unit, an optical transmitting module.

Each of the M receiving blocks contains a receiving optical module, a converter of the physical sequence into a logical pulse sequence, an SDH demultiplexer, a PDH group signal disassembling unit (tribe), a decoder that converts the PCM sequence into an output signal.

The device operates as follows.

The channel-forming unit combines the data arriving at its inputs (channels) and encodes them. To combine the signals, a time multiplexer is used, the main node of which is the switch. The switch sequentially connects each input channel for a specific time interval (time slot) to the output. The stream of samples thus formed from different input channels is encoded and sent to the communication channel to increase the noise immunity. On the receiving side, the demultiplexer, using a similar switch, low-pass filters and a decoder, extracts individual samples from the group signal and distributes them along the corresponding channels. It is important that the switches on the transmitting and receiving sides must work synchronously, i.e. must be synchronized.

The synchronization process is reduced to the insertion of either an additional (synchronizing or equalizing) bit, or group of bits, after m samples, or organizing a more complex repeating structure in the sample stream, including m samples and k fields of a certain length or equalizing bits. This structure is fixed and is called a frame, or frame, or "cycle". Several frames can be combined into an even more general structure called a "supercycle".

At the upper levels of the hierarchy, internal bitwise synchronization is used, in which the multiplexer itself aligns the input stream velocities by adding the necessary number of equalizing bits to channels with relatively lower transmission rates. These bits are then deleted by demultiplexing at the receiving side to restore the original digital sequence. Such a transmission process was called plesiochronous (i.e., almost synchronous), and the digital hierarchy, respectively, is the name of the plesiochronous digital hierarchy PDI (PDH).

The PDI signals are fed through the level matching unit to the SDH multiplexer.

SDH multiplexers (SONET) are designed to support only those access channels whose transmission speed corresponds to the integrated standard series of PDH hierarchies, namely: 1.5; 2; 6; 34; 45; 140 Mbps, or T1, E1, T2, E3, T3, E4. Digital signal streams, the transmission speed of which corresponds to this series, are called PDH tribes or component signals, and signals whose transmission speed corresponds to the standard SONET / SDH series of speeds are called SONET / SDH tribes.

PDH tribes are packaged in the STM-N module so that they can be displayed in the right place. For this, the module should be in the form of a standard-size container with a header, which contains all the information necessary for its management and routing. The internal capacity of the module should be sufficient to accommodate the payload - smaller containers of the same type, which should also have a header and payload, etc. (by the principle of sequential investments or encapsulation). A container is used to carry information, i.e. is a logical and not a physical object, therefore it is called a virtual container. So, one of the functions of the SDH multiplexer is the packing of tribes into standard labeled containers, the sizes of which are determined by the level of the tribe in the PDH hierarchy.

Virtual containers are grouped together. The lower level containers are multiplexed and used as the payload of the upper level containers, which, in turn, serve as the payload of the container of the highest level - the STM-1 frame. Such grouping is carried out according to a rigid synchronous scheme, in which the place of an individual container in the field to accommodate the load is strictly fixed. From several frames, new (larger) formations - multiframes can be composed. As a result of possible differences in the type of constituent containers and temporary fluctuations during the loading of the frame, the position of the containers inside the multiframe may change, which may lead to an error during the input / output of the container. To eliminate this fact, a pointer is set up for each virtual container containing the actual address of the start of the virtual container on the map of the field allocated for the payload. The pointer gives the container some degree of freedom, i.e. the ability to "swim" under the influence of unforeseen time delays, but at the same time ensures that it will not be lost.

The SDH multiplexer assigns a pointer to containers, which eliminates the contradiction between the fact of processing synchronization and a possible change in the position of the container inside the payload field. Although the sizes of the containers are different, and the capacity of the containers of the upper levels is quite large, it may turn out that it is still insufficient, or it is better to select several smaller containers under load. To do this, the SDH technology provides for the possibility of coupling or docking containers (composing several containers together into one structure, called a composite container or coupler). A composite container is considered (in terms of load placement) as one large container.

Containers are the first elements in the list of elements in the SDH hierarchy. A route (or path) header is added to the container. As a result, it turns into a virtual container of VC level n, i.e. Vc-n. The following virtual containers exist: VC-1, VC-2 - virtual containers of the lower levels 1 or 2 and VC-3, VC-4 - virtual containers of the upper levels 3 or 4, the format of which is determined by the formula: RON + PL, where RON is the route heading PL is the payload. Virtual containers VC-1, VC-3 of levels 1, 3 are divided into virtual containers of sublevels nm, i.e. VC-nm, namely: VC-1 is divided into VC-11 and VC-12, VC-3 is divided into VC-31 and VC-32.

The digital binary-coded PCM sequence generated as a result of multiplexing is fed into the communication channel, at the input of which the interface device and transmitter (optical transmitting module) are used. Given that the transmission channel is optical, the resulting sequence has to be re-encoded at least twice to optimize its passage through the communication line. For this, a linear coding unit is used in the device.

The bit stream obtained as a result of quantization and binary coding (codification) is optimal only from the point of view of reducing quantization errors, but is not suitable for transmission over a communication channel for a number of reasons, the main of which are as follows:

- the output digital stream has a wide range, which complicates its transmission over the communication channel and synchronization,

- the signal spectrum has low-frequency components that can interfere with the same components of the transmitted signal,

- the signal spectrum contains a large constant component, complicating the filtering of the supply voltage.

To optimize the spectrum of the signal supplied to the communication line, the so-called linear coding is used. It should provide:

- minimum spectral density at zero frequency,

- easy allocation of the clock frequency of the transmitted signal against the background of the continuous part of the spectrum,

- the continuous spectrum should be narrow enough for transmission through the communication channel without distortion,

- low redundancy,

- the minimum possible lengths of blocks of repeating characters ("1" or "0") and disparity (inequality in the number of elements "1" and "0" in code combinations).

For binary coding, the number of input signal levels is m = 2, and the number of output signal levels n can be 2 (two-level encoding) or 3 (three-level encoding). Two-level coding can be unipolar (+1, 0) and bipolar or symmetric (+1, -1); three-level - unipolar (+2, +1, 0) and bipolar (+1, 0, -1). Optical communication lines require unipolar coding techniques. To limit the length of blocks of repeating symbols of the type "11 ... 11" or "00 ... 00", an inversion ("reversal" or an unplanned (intentional) change) of the pulse polarity of the regular code sequence is used. Along with inversion, inserts (additional characters of a certain polarity) are sometimes used to preserve the parity of the code combination. Coding algorithms are described by a directional state graph that reflects the set of all possible states and transitions from one state to another.

Optical pulses from the output of the transmitting optical module are directed to the input optical pole of the wave multiplexer, which is an optical combiner with a transmission matrix N X 1, where N is the number of combined digital streams generated by the method described above.

A powerful optical amplifier (booster), an optical linear amplifier, and an optical preamplifier are optional units that amplify the optical digital sequence to the level required to create the necessary total power budget in the optical transmission channel.

A wave demultiplexer or a spectrally selective splitter is installed at the output of the transmission channel. Digital optical streams allocated by the demultiplexer are processed in the reverse order.

An optical photodetector receives a signal.

The converter of the physical sequence into a logical pulse sequence equivalent to the STM-N module performs all the necessary inverse transformations to decode the interface code and interpret the headers: sectional, multiplexed, and path (path).

The SDH demultiplexer performs logical decomposition of the pulse sequence of the STM-N module and extracts component signals (tribes) of the required level of the PDH hierarchy.

The disassembling unit of the group signal (frame / tribe) PDH of the received hierarchy level to the required one, for example E1, selects the necessary time slots.

The decoder converts the PCM sequence into an output signal; for this, noise-resistant decoding and reconstruction of the sampled, quantized, and codified signal is performed.

The disadvantages of the considered method and device are associated with numerous transcodes. It:

- low noise immunity,

- complexity and high cost,

- low transmission rate of useful information,

- increased message redundancy.

The proposed method and device solves the problem of increasing the noise immunity and reliability of the transmitted information, simplifying and lowering the cost, increasing the transmission rate of useful information, reducing the redundancy of the transmitted signals.

The essence of the invention lies in the fact that

1. In the method for transmitting discrete information on an optical channel, which consists in the fact that M N-bit digital data in a parallel code is multiplexed (combined) into a group bit sequence, converted into optical pulses, sent to an optical communication channel, at the other end of the channel the bonds are converted into electrical impulses and demultiplexed (decompress), multiplexing (combining) and demultiplexing (decompression) are performed in the optical range by delaying a fixed interval and time and converting wavelength of optical radiation.

2. To a device containing M transmitting units connected to M receiving units through sequentially mounted optical combiner with a transmission matrix M X 1, an optical connector, a fiber optic path, a second optical connector, an optical spectrally selective coupler with a transmission matrix 1 X M and each of the M transmitting blocks contains N transmitting optical modules, and each of the M receiving blocks contains N receiving optical modules,

- M transceiving optical modules connecting the output optical poles of M transmitting units and the input optical poles of the optical combiner, M transceiving optical modules connecting the output optical poles of a spectrally selective splitter and the input optical poles of M receiving units have been introduced;

- the input buffer N bit register is entered into the transmitting blocks, the information bits (data) are fed to its input port, the control input of which is connected to the synchronization device, the output port of the buffer register is connected to the control inputs of N transmitting optical modules, (N + 1) a transmitting optical module, the control input of which is connected to the output of the synchronization device, an optical combiner with a transmission matrix (N + 1) X1, the input optical poles of which are connected to the output optical poles of the transmitting optical FIR modules through a fiber optic delay line and the output terminal is the output of the optical transmitter unit;

- an optical splitter with a transmission matrix 1X (N + 1) is introduced into the receiving blocks, the input optical pole of which is the input of the receiving block, and the output optical poles are connected to the optical input poles of the photodetector modules via fiber-optic delay lines, the output buffer N bit register, D-trigger, pulse shaper, time delay device, wherein the input port of the buffer register is connected to the outputs of the N first photodetector modules, the control input of the register is connected to the output of the pulse shaper ow and the input of the time delay device connected by its output to the reset input of the D-trigger, the data input of the D-trigger is connected to the logic unit level, the clock input of the D-trigger is connected to the output of the (N + 1) -th photodetector module, and the output port of the buffer register connected to the receiver of information.

Figure 1 shows a structural diagram of a transmitting unit of a device that implements the proposed method and device.

The transmitting unit consists of:

- input buffer two-port N-bit register 1,

- synchronization devices 2,

- (N + 1) semiconductor laser transmitting modules 3,

- (N + 1) fiber optic delay lines 4,

- optical combiner 5 with a transmission matrix (N + 1) X1.

The transmitting unit operates as follows:

Digital data prepared for transmission via a fiber-optic transmission channel in the form of an N-bit word is fed to the input port of the input buffer register 1. Data is written, the stored data is output to the output port, and the high impedance state of the output port of register 1 is turned off by the output signal of the device synchronization 2, and recording is performed on the leading edge of the pulse, disabling the third state and outputting data on the level of the synchronization signal.

The outputs of the output port of the register 1 and the output of the synchronization device 2 are connected to the control inputs of the semiconductor laser transmitting modules 3. The first N modules of the transmitting modules 3 are controlled by the data of the output port of the register 1. The (N + 1) th module is controlled by the synchronization device. All semiconductor laser transmitting modules can operate at the same wavelength of optical radiation.

The semiconductor laser transmitting modules 3 convert the electrical signals into optical and direct these signals to the input poles of the set of fiber-optic delays 4. The optical synchronization signal (I _s ) is delayed by the (N + 1) -th delay line and has a minimum, determined by the length of the connecting cables, a delay. We will consider it equal to 0. The optical signal modulated by the first (least significant) bit of information (I ₁ ) is delayed by the first delay line for a time Δt, the second bit of information is delayed by the second delay line - for a time 2Δt, and so on. The optical signal modulated by the last (oldest) Nth bit of information is delayed by the time · NΔt.

The output poles of the set of fiber-optic delay lines 4 are connected to the input poles of the optical combiner 5. The combiner generates a group optical signal directed to the output of the transmitting unit.

The diagrams presented in figure 2 illustrates the process of generating a group optical signal by the example of transmitting a 4-bit hexadecimal number 0AN = 1010V using the proposed transmitting unit.

The electrical information signals (D ₁ ... D ₄ ) and the synchronization signal (U _c ) at the inputs of the transmitting laser optical modules 3 are shown in diagrams “a”. The optical information signals (I ₁ ... I ₄ ) and the optical synchronization signal (I _c ) at the outputs of the set of delays 4 are shown in diagrams “b”. The synchronization signal (I _s ) has a minimum delay, it can be taken equal to 0. The first bit of information (I ₁ ) is delayed by the time Δt. The second bit of information (I ₂ ) is delayed by 2Δt, the third by 3Δt, and the fourth by 4Δt. In diagram "c" a group optical signal is presented at the output pole of combiner 5. All signals are generated at the same wavelength of optical radiation.

Figure 3 shows the structural diagram of the receiving unit of the device in question.

The receiving unit consists of an optical splitter 6 with a transmission matrix 1 X N, a set of fiber-optic delay lines 7 of (N + 1) delay lines, a set of (N + 1) photodetector modules 8, an output two-port N-bit buffer register 9, D-trigger 10, pulse shaper 11, time delay device 12.

The receiving unit operates as follows:

The group optical signal hits the input optical pole of the splitter 6 with the transmission matrix 1X (N + 1).

The output poles of the splitter 6 are connected to the input optical poles of a set of fiber optic delay lines 7, consisting of (N + 1) delay lines. The set of delay lines 7 is structurally similar to the set 4 located in the transmitting unit, but in the synchronization channel, the delay is maximum and equal to (Δt · N-τ), where τ is the time interval that takes into account the speed of the used component base. In the transmission channel of the first bit of information (I ₁ ), the delay is Δt · (N-1), the second is Δt · (N-2), and so on. The most significant bit of information has a minimum delay, we take it equal to 0. The output poles of the delay lines 7 are connected to the optical inputs of the set of photodetector modules 8, consisting of (N-1) modules. The electrical outputs of the photodetector modules (1 ÷ N) are connected to the lines of the input port of the buffer register 9. The output of the (N + 1) -th photodetector module is connected to the clock input of the D-trigger 8, the data input of which is connected to a voltage with a logic level of one. On the edge of the signal at the clock input at the output of the trigger 8 appears a voltage step. This step is supplied to the pulse shaper 11, which generates a pulse at the leading edge of the signal at its input that is equal to the duration of the synchronization signal. This pulse is directed to the input synchronization, control the output and turn off the high-impedance (third) state of the outputs of the output port of the register 9 and the device time delay 12.

By design, register 9 is similar to register 5 located in the transmitting unit. Information is recorded in register 9 on the leading edge of the pulse generated by the driver 11, and the third state of the output port is turned off and the recorded data is output to the output port by its level.

At the time of the presence of the synchronization signal from the output of the shaper 11 at the control input of the register 9 at its outputs are set data that is read by consumers of information.

The pulse from the output of the time delay device 12 after a time interval longer than N (2Δt + t _c ), where t _c is the duration of the synchronization pulse, resets trigger 10 to its original state to receive a new block of information.

The reception of information by the receiving unit is illustrated by the example of transmitting a 4-bit data word, which is discussed above, using the diagrams presented in figure 4.

The optical group signal at the input of the splitter 6 repeats the signal at the output of the combiner 5 (see diagram "c" in figure 2) and is shown on the diagram "a" see figure 4. The shape of the output signals of the splitter 6 repeats the shape of the group optical signal at its input. The output poles of the optical splitter 6 are optically connected to the input optical poles of the set of fiber optic delay lines 7. The output optical poles of the delay lines 7 are connected to the optical input poles of the set of photodetector modules 8. The optical group signals from the output of the splitter are converted by the photodetector modules into electrical form. Plots of electrical signals at the output of the photodetector modules are shown in plots "b" and "c". Plots "b" show signals in the information channels, and plots "c" show signals in the synchronization path. In the transmission channel of the first bit of information, the signals are delayed by 3Δt, the second bit by 2Δt, and the third bit by Δt. In the transmission channel of the fourth bit of information, the signals are practically not delayed. The signals in the synchronization path are delayed for a time (4Δt-τ). The first in the group signal is a synchronization pulse, this pulse with a rising edge sets the output of the trigger 10 signal of a logical unit. The waveform of this signal is shown in diagram "d". The output signal of the trigger 10 triggers its front pulse generator 11, which controls the recording of data in the register 9 and the state of the output lines of this register. The shape of the output pulse of the shaper 11 is presented on the plot "e". The response time of the trigger 10 and the pulse shaper 11 is taken into account the component of the delay time in the synchronization path - τ.

As follows from diagrams “b” and “e”, the pulse at the output of the former 11 “latches” half a byte of information in register 9, see diagram “f”. This nibble is set on the register output lines and can be read. As follows from the diagrams, the output data of the buffer register 9 received on the optical transmission channel coincide with the sent data (see diagram "a" in figure 2).

The pulse delayed by the time delay device 12, after the end of the group optical signal, resets the trigger 10 to its original state.

Figure 5 shows the structural diagram of the entire device that implements the proposed method and device (interface).

The device consists of M transmitting units 13, discussed above, the first group of M transceiving optical modules 14, an optical combiner 15 with a transmission matrix M X 1, the output optical pole of which is connected through the connector 16 to the input optical pole of the fiber optic path 17, the output optical the pole of which is connected to the input optical pole of a spectrally selective coupler 18 with a transmission matrix 1 X M using an optical connector 19, the second group of M transceiving optical modules 20, M p iemnyh units 21 discussed above.

The device operates as follows.

Group digital optical information flows from the M transmitting units 13 are fed to the input optical poles of the M transceiver semiconductor optical modules 14. The operation of the transmitting units was discussed above. Each transceiver module consists of a receiving and transmitting optical module, and the output of the receiving optical module is connected to the input of the transmitting optical module. An optical signal with one radiation wavelength is received, and transmitted with another, characteristic of each of the M data streams. The output optical poles of the transceiver modules are connected to the input optical poles of the optical combiner 15, combining them into a single information stream. The spectrum of this stream consists of M spectral channels corresponding to the standard series. A single information stream is routed through the optical connector 16 to the fiber optic path 17, and then through the optical connector 19 to the input optical pole of the spectrally selective coupler 18. The spectrally selective coupler 18 acts as a switch that distributes a single information stream between consumers (subscribers) in depending on the wavelength of the optical signal. Local optical information flows are directed to the inputs of the M transceiver modules 20 necessary to restore the required signal-to-noise ratio (restore energy balance). The output optical poles of the transceiver modules 20 are connected to the input optical poles M of the receiving units 21, the operation of which is discussed above. The output radiation of the modules 20 may be of the same wavelength.

The considered device that implements the proposed method and device has the following advantages compared to the prototype device.

1. The best noise immunity in the presence of impulse noise, since the device has a minimum number of electronic nodes, there are no nodes for the electronic conversion of a parallel code to a serial one and vice versa using shift registers subject to impulse noise.

2. The simplicity of the design of electronic components compared to prototype devices is less and they are simpler, therefore, the lower cost of the entire device.

3. Higher speed of information transfer due to the possibility of parallel transmission of several bytes of information and less redundancy of messages.

Consider an example for comparing the transfer rate of useful information using the proposed interface and the Fiber Channel (FC) interface.

Let the discrete information be transmitted through an optical transmission channel with one of the standard speeds for the FC interface - 1.06 Gbit / s.

FCs have the following structure:

Frame start marker Headline Optional title (optional field) Data (payload) CRC code (parity check) End of frame marker 4 bits 24 bits 512 bit Maximum - 2048 bits 32 bits 32 bits

Only part of the frame bits carries useful information, taking this into account, the transmission rate of useful information F _u can be found by the formula

where F _k - channel speed, determined by the speed of the receiving and transmitting optical modules (F _k = 1,06 Gbit / s),

N - bit depth of the transmitted word (in this example, N = 8, 128, 256),

L ₁ is the length in bits of the start marker (L ₁ = 4);

L ₂ is the length in bits of the header (L ₂ = 24);

L ₃ is the bit length of the additional header (L ₃ = 0);

L ₄ is the length in bits of the CRC code (L ₄ = 32);

L ₅ is the length in bits of the end marker (L ₅ = 32);

Suppose that the same information is transmitted using the proposed interface. Given that information with different wavelengths is transmitted in parallel with minimal redundancy, the transmission rate of useful information F _u can be found by the formula

where N is the bit depth of the transmitted word (in the considered example, N = 8),

M - the number of served subscribers (sources of information), M = 1, 16, 32;

F _k - channel speed, (F _k = 1,06 Gbit / s).

The table shows the results of calculations performed by formulas (1) and (2) for the considered example.

Number of sources of information The transmission rate of useful information (at a transmission channel speed of 1060 Mbit / s), MB / s For FC interface For the proposed interface one 10.6 62.3 16 77.1 997.6 32 97.5 1995,3

The table shows that the proposed interface has advantages in the transmission rate of useful information compared to the FC interface.

Since the rest of the considered interfaces, and this is the interface according to the G.703 protocol; Ethernet, Fast Ethernet, Gigabit Ethernet, FDDI, ATM (SONET), convert the parallel code into a bit sequence, encode it, combine it into packets (frames, tribes, frames) having service fields that do not carry useful information, it can be shown that the proposed the interface will provide a higher transmission rate of useful information at the same maximum channel speed and in comparison with these interfaces.

Information sources

1. Slepov N.N. Modern technologies of digital fiber-optic communication networks, M .: Radio and communications, 2000, 467 p.

2. Information from the site "TELECOMMUNICATIONS: help system" ^TM : http://www.opticovolokno.narod.ru/list/chastl.html.

3. A.Shitikov Fiber optic lines and communications, "Chip News" No. 4, 2002

4. Description of the MAX3691 chip at http://pdfserv.maxim-ic.com/en/ds/MAX3691.pdf.

5. Description of the MAX3675 microcircuit on the site http://pdfserv.maxim-ic.com/en/ds/MAX3675.pdf.

6. Description of the MAX3681 chip on the website http://pdfserv.maxim-ic.com/en/ds/MAX3681.pdf.

7. Sklyarov O.K. Fiber-optic networks and communication systems, Moscow: Solon-press, 2004, 266 p.

8. K. Yonenaga, A. Hirano, S. Kuwabara. Temperature - independent 80 Gbit / s OTDM transmission line. ECOC'99, Nice, 1999.

9. Fiber-optic technology: history, achievements, prospects - Collection of articles edited by Dmitriev SA, Slepova NN, JSC "Fiber-optic technology", publishing house "Connect", 2000

Claims (2)

1. A method for transmitting discrete information on an optical channel, which consists in the fact that MN-bit digital data in parallel code is multiplexed (combined) into a group bit sequence, converted into optical pulses, sent to an optical communication channel, converted at the other end of the communication channel into electrical pulses and demultiplex (decompress), characterized in that the MN-bit digital data in parallel code is converted into M X N optical signals, and multiplex (combine) and demultiple siruyut (decompact) of the optical delay range by fixed time intervals and converting wavelength of optical radiation. 2. A device for transmitting discrete information on an optical channel, containing M transmitting units connected to M receiving units through sequentially mounted optical combiner with a transmission matrix M X 1, an optical connector, a fiber optic path, a second optical connector, an optical spectrally selective coupler with transmission matrix 1 X M, and each of the M transmitting blocks contains a transmitting optical module, and each of the M receiving blocks contains a receiving optical module, different m that M transceiving optical modules connecting the output optical poles of the M transmitting units and the input optical poles of the optical combiner, M transceiving optical modules connecting the output optical poles of a spectrally selective coupler and the input optical poles of the M receiving units are inserted into it; input buffer N-bit register, N transmitting optical modules, an optical combiner with a transmission matrix (N + 1) X1, (N + 1) fiber-optic delay lines, the input port of the buffer register connected to the information source controlling the register input is connected to the output of the synchronization device, which is simultaneously connected to the control input of the (N + 1) -th transmitting optical module, the output port of the buffer register is connected to the control inputs of the remaining transmitting optical modules, optical outputs s optical transmission modules are connected with the poles of the input optical combiner via a fiber optic delay line, and an optical output terminal of the combiner is the optical output of the transmitting unit; an optical splitter with a transmission matrix 1X (N + 1) is introduced into the receiving blocks, the input optical pole of which is the input of the receiving block, and the output optical poles are connected to the optical input poles of the photodetector modules via fiber-optic delay lines, the output buffer N-bit register, D-trigger, pulse shaper, time delay device, and the input port of the buffer register is connected to the outputs of the N first photodetector modules, the control input of the register is connected to the output of the pulse shaper s and the input of the time delay device connected by its output to the reset input of the D-trigger, the data input of the D-trigger is connected to the logic unit level, the clock input of the D-trigger is connected to the output of the (N + 1) -th photodetector module, and the output port of the buffer register connected to the receiver of information.

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