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76-462: Hibernia's network provided service, from 2.5 Gbit/s to 100 Gbit/s wavelengths and Ethernet from 10 Mbit/s to 100 Gbit/s. It also provided traditional SONET/SDH services. In January 2017, the company was acquired and absorbed into GTT Communications, Inc. It was previously a subsidiary of Columbia Ventures Corporation (CVC) and was owned by both CVC and Constellation Ventures Partners. Hibernia Networks' transatlantic cable system

152-588: A high-speed side (where the full line rate signal is supported), and a low-speed side , which can consist of electrical as well as optical interfaces. The low-speed side takes in low-speed signals, which are multiplexed by the network element and sent out from the high-speed side, or vice versa. Recent digital cross connect systems (DCSs or DXCs) support numerous high-speed signals, and allow for cross-connection of DS1s, DS3s and even STS-3s/12c and so on, from any input to any output. Advanced DCSs can support numerous subtending rings simultaneously. SONET and SDH have

228-416: A voltage or current (depending on type) that represents the value presented on their digital inputs. This output would then generally be filtered and amplified for use. To recover the original signal from the sampled data, a demodulator can apply the procedure of modulation in reverse. After each sampling period, the demodulator reads the next value and transitions the output signal to the new value. As

304-483: A 'transport' in the OSI Model sense). Due to SONET/SDH's essential protocol neutrality and transport-oriented features, SONET/SDH was the choice for transporting the fixed length Asynchronous Transfer Mode (ATM) frames also known as cells. It quickly evolved mapping structures and concatenated payload containers to transport ATM connections. In other words, for ATM (and eventually other protocols such as Ethernet ),

380-410: A DS0 is either μ-law (mu-law) PCM (North America and Japan) or A-law PCM (Europe and most of the rest of the world). These are logarithmic compression systems where a 12- or 13-bit linear PCM sample number is mapped into an 8-bit value. This system is described by international standard G.711 . Where circuit costs are high and loss of voice quality is acceptable, it sometimes makes sense to compress

456-485: A NRZ system to be synchronized using in-band information, there must not be long sequences of identical symbols, such as ones or zeroes. For binary PCM systems, the density of 1-symbols is called ones-density . Ones-density is often controlled using precoding techniques such as run-length limited encoding, where the PCM code is expanded into a slightly longer code with a guaranteed bound on ones-density before modulation into

532-407: A PCM stream , the amplitude of the analog signal is sampled at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Alec Reeves , Claude Shannon , Barney Oliver and John R. Pierce are credited with its invention. Linear pulse-code modulation ( LPCM ) is a specific type of PCM in which the quantization levels are linearly uniform. This

608-508: A PDH DS1 signal. A VTG may instead be subdivided into three VT2 signals, each of which can carry a PDH E1 signal. The SDH equivalent of a VTG is a TUG-2; VT1.5 is equivalent to VC-11, and VT2 is equivalent to VC-12. Three STS-1 signals may be multiplexed by time-division multiplexing to form the next level of the SONET hierarchy, the OC-3 (STS-3), running at 155.52 Mbit/s. The signal

684-409: A SONET/SDH signal allows it to carry many different services in its virtual container (VC), because it is bandwidth-flexible. SONET and SDH often use different terms to describe identical features or functions. This can cause confusion and exaggerate their differences. With a few exceptions, SDH can be thought of as a superset of SONET. SONET is a set of transport containers that allow for delivery of

760-455: A larger aggregate data stream , generally for transmission of multiple streams over a single physical link. One technique is called time-division multiplexing (TDM) and is widely used, notably in the modern public telephone system. The electronics involved in producing an accurate analog signal from the discrete data are similar to those used for generating the digital signal. These devices are digital-to-analog converters (DACs). They produce

836-585: A limited number of architectures defined. These architectures allow for efficient bandwidth usage as well as protection (i.e. the ability to transmit traffic even when part of the network has failed), and are fundamental to the worldwide deployment of SONET and SDH for moving digital traffic. Every SDH/SONET connection on the optical physical layer uses two optical fibers, regardless of the transmission speed. Linear Automatic Protection Switching (APS), also known as 1+1 , involves four fibers: two working fibers (one in each direction), and two protection fibers. Switching

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912-589: A rate above 3500–4300 Hz; lower rates proved unsatisfactory. In 1920, the Bartlane cable picture transmission system used telegraph signaling of characters punched in paper tape to send samples of images quantized to 5 levels. In 1926, Paul M. Rainey of Western Electric patented a facsimile machine that transmitted its signal using 5-bit PCM, encoded by an opto-mechanical analog-to-digital converter . The machine did not go into production. British engineer Alec Reeves , unaware of previous work, conceived

988-552: A result of these transitions, the signal retains a significant amount of high-frequency energy due to imaging effects. To remove these undesirable frequencies, the demodulator passes the signal through a reconstruction filter that suppresses energy outside the expected frequency range (greater than the Nyquist frequency f s / 2 {\displaystyle f_{s}/2} ). Common sample depths for LPCM are 8, 16, 20 or 24 bits per sample . LPCM encodes

1064-505: A single sound channel. Support for multichannel audio depends on file format and relies on synchronization of multiple LPCM streams. While two channels (stereo) is the most common format, systems can support up to 8 audio channels (7.1 surround) or more. Common sampling frequencies are 48 kHz as used with DVD format videos, or 44.1 kHz as used in CDs. Sampling frequencies of 96 kHz or 192 kHz can be used on some equipment, but

1140-646: A time. Rather than natural binary, the grid of Goodall's later tube was perforated to produce a glitch-free Gray code and produced all bits simultaneously by using a fan beam instead of a scanning beam. In the United States, the National Inventors Hall of Fame has honored Bernard M. Oliver and Claude Shannon as the inventors of PCM, as described in "Communication System Employing Pulse Code Modulation", U.S. patent 2,801,281 filed in 1946 and 1952, granted in 1956. Another patent by

1216-485: A variety of protocols, including traditional telephony, ATM, Ethernet, and TCP/IP traffic. SONET therefore is not in itself a native communications protocol and should not be confused as being necessarily connection-oriented in the way that term is usually used. The protocol is a heavily multiplexed structure, with the header interleaved between the data in a complex way. This permits the encapsulated data to have its own frame rate and be able to "float around" relative to

1292-466: Is 10 Gigabit Ethernet (10GbE). The Gigabit Ethernet Alliance created two 10 Gigabit Ethernet variants: a local area variant ( LAN PHY ) with a line rate of 10.3125 Gbit/s, and a wide area variant ( WAN PHY ) with the same line rate as OC-192/STM-64 (9,953,280 kbit/s). The WAN PHY variant encapsulates Ethernet data using a lightweight SDH/SONET frame, so as to be compatible at a low level with equipment designed to carry SDH/SONET signals, whereas

1368-491: Is added, and that SONET network element (NE) is said to be a path generator and terminator . The SONET NE is line terminating if it processes the line overhead. Note that wherever the line or path is terminated, the section is terminated also. SONET regenerators terminate the section, but not the paths or line. An STS-1 payload can also be subdivided into seven virtual tributary groups (VTGs). Each VTG can then be subdivided into four VT1.5 signals, each of which can carry

1444-505: Is based on the line state, and may be unidirectional (with each direction switching independently), or bidirectional (where the network elements at each end negotiate so that both directions are generally carried on the same pair of fibers). Pulse-code modulation Pulse-code modulation ( PCM ) is a method used to digitally represent analog signals . It is the standard form of digital audio in computers, compact discs , digital telephony and other digital audio applications. In

1520-516: Is composed as follows: Data transmitted from end to end is referred to as path data . It is composed of two components: For STS-1, the payload is referred to as the synchronous payload envelope (SPE), which in turn has 18 stuffing bytes, leading to the STS-1 payload capacity of 756 bytes. The STS-1 payload is designed to carry a full PDH DS3 frame. When the DS3 enters a SONET network, path overhead

1596-545: Is considered a variation of SDH because of SDH's greater worldwide market penetration. SONET is subdivided into four sublayers with some factor such as the path, line, section and physical layer. The SDH standard was originally defined by the European Telecommunications Standards Institute (ETSI), and is formalised as International Telecommunication Union (ITU) standards G.707, G.783 , G.784, and G.803. The SONET standard

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1672-508: Is dictated by the bandwidth requirements for PCM-encoded telephonic voice signals: at this rate, an STS-1/OC-1 circuit can carry the bandwidth equivalent of a standard DS-3 channel, which can carry 672 64-kbit/s voice channels. In SONET, the STS-3c signal is composed of three multiplexed STS-1 signals; the STS-3c may be carried on an OC-3 signal. Some manufacturers also support the SDH equivalent of

1748-484: Is for path overhead; it is followed by the payload container, which can itself carry other containers. Administrative units can have any phase alignment within the STM frame, and this alignment is indicated by the pointer in row four. The section overhead (SOH) of a STM-1 signal is divided into two parts: the regenerator section overhead (RSOH) and the multiplex section overhead (MSOH). The overheads contain information from

1824-486: Is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm ). Though PCM is a more general term, it is often used to describe data encoded as LPCM. A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the sampling rate , which is the number of times per second that samples are taken; and

1900-503: Is interleaved with it during transmission. Part of the overhead is transmitted, then part of the payload, then the next part of the overhead, then the next part of the payload, until the entire frame has been transmitted. In the case of an STS-1, the frame is 810 octets in size, while the STM-1/STS-3c frame is 2,430 octets in size. For STS-1, the frame is transmitted as three octets of overhead, followed by 87 octets of payload. This

1976-524: Is multiplexed by interleaving the bytes of the three STS-1 frames to form the STS-3 frame, containing 2,430 bytes and transmitted in 125  μs . Higher-speed circuits are formed by successively aggregating multiples of slower circuits, their speed always being immediately apparent from their designation. For example, four STS-3 or AU4 signals can be aggregated to form a 622.08 Mbit/s signal designated OC-12 or STM-4 . The highest rate commonly deployed

2052-408: Is repeated nine times, until 810 octets have been transmitted, taking 125  μs . In the case of an STS-3c/STM-1, which operates three times faster than an STS-1, nine octets of overhead are transmitted, followed by 261 octets of payload. This is also repeated nine times until 2,430 octets have been transmitted, also taking 125  μs . For both SONET and SDH, this is often represented by displaying

2128-596: Is the OC-768 or STM-256 circuit, which operates at rate of just under 38.5 Gbit/s. Where fiber exhaustion is a concern, multiple SONET signals can be transported over multiple wavelengths on a single fiber pair by means of wavelength-division multiplexing , including dense wavelength-division multiplexing (DWDM) and coarse wavelength-division multiplexing (CWDM). DWDM circuits are the basis for all modern submarine communications cable systems and other long-haul circuits. Another type of high-speed data networking circuit

2204-407: Is the lowest SONET layer and it is responsible for transmitting the bits to the physical medium. The section layer is responsible for generating the proper STS-N frames which are to be transmitted across the physical medium. It deals with issues such as proper framing, error monitoring, section maintenance, and orderwire. The line layer ensures reliable transport of the payload and overhead generated by

2280-444: Is transmitted in exactly 125  μs , therefore, there are 8,000 frames per second on a 155.52 Mbit/s OC-3 fiber-optic circuit. The STM-1 frame consists of overhead and pointers plus information payload. The first nine columns of each frame make up the section overhead and administrative unit pointers, and the last 261 columns make up the information payload. The pointers (H1, H2, H3 bytes) identify administrative units (AU) within

2356-652: The SIGSALY encryption equipment, conveyed high-level Allied communications during World War II . In 1943 the Bell Labs researchers who designed the SIGSALY system became aware of the use of PCM binary coding as already proposed by Reeves. In 1949, for the Canadian Navy's DATAR system, Ferranti Canada built a working PCM radio system that was able to transmit digitized radar data over long distances. PCM in

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2432-652: The bit depth , which determines the number of possible digital values that can be used to represent each sample. Early electrical communications started to sample signals in order to multiplex samples from multiple telegraphy sources and to convey them over a single telegraph cable. The American inventor Moses G. Farmer conceived telegraph time-division multiplexing (TDM) as early as 1853. Electrical engineer W. M. Miner, in 1903, used an electro-mechanical commutator for time-division multiplexing multiple telegraph signals; he also applied this technology to telephony . He obtained intelligible speech from channels sampled at

2508-474: The public switched telephone network (PSTN) had been largely digitized with very-large-scale integration (VLSI) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges , user-end modems and a wide range of digital transmission applications such as the integrated services digital network (ISDN), cordless telephones and cell phones . PCM is the method of encoding typically used for uncompressed digital audio. In

2584-679: The Atlantic. In 2011, Hibernia announced its expansion into the Pacific Rim with network connectivity into Tokyo, Singapore and Hong Kong. In August 2012, the company acquired the Media Connect assets from TeliaSonera International Carrier (TSIC), located in Europe and the US, and rebranded as Hibernia Networks. This made Hibernia Networks one of the largest DTM Video Transport Networks in

2660-559: The LAN PHY variant encapsulates Ethernet data using 64B/66B line coding. However, 10 Gigabit Ethernet does not explicitly provide any interoperability at the bitstream level with other SDH/SONET systems. This differs from WDM system transponders, including both coarse and dense wavelength-division multiplexing systems (CWDM and DWDM) that currently support OC-192 SONET signals, which can normally support thin-SONET–framed 10 Gigabit Ethernet. User throughput must not deduct path overhead from

2736-505: The Q3 interface protocol suite defined in ITU recommendations Q.811 and Q.812. With the convergence of SONET and SDH on switching matrix and network elements architecture, newer implementations have also offered TL1. Most SONET NEs have a limited number of management interfaces defined: To handle all of the possible management channels and signals, most modern network elements contain a router for

2812-484: The SDH/SONET frame structure and rate. This interleaving permits a very low latency for the encapsulated data. Data passing through equipment can be delayed by at most 32  microseconds  (μs), compared to a frame rate of 125 μs; many competing protocols buffer the data during such transits for at least one frame or packet before sending it on. Extra padding is allowed for the multiplexed data to move within

2888-467: The STS-1/OC-1, known as STM-0. In packet-oriented data transmission, such as Ethernet , a packet frame usually consists of a header and a payload . The header is transmitted first, followed by the payload (and possibly a trailer , such as a CRC ). In synchronous optical networking, this is modified slightly. The header is termed the overhead , and instead of being transmitted before the payload,

2964-458: The STS-3c is carried over OC-3, it is often colloquially referred to as OC-3c , but this is not an official designation within the SONET standard as there is no physical layer (i.e. optical) difference between an STS-3c and 3 STS-1s carried within an OC-3. SONET offers an additional basic unit of transmission, the STS-1 (Synchronous Transport Signal 1) or OC-1 , operating at 51.84 Mbit/s—exactly one third of an STM-1/STS-3c/OC-3c carrier. This speed

3040-569: The amount of buffering required between elements in the network. Both SONET and SDH can be used to encapsulate earlier digital transmission standards, such as the PDH standard, or they can be used to directly support either Asynchronous Transfer Mode (ATM) or so-called packet over SONET/SDH (POS) networking. Therefore, it is inaccurate to think of SDH or SONET as communications protocols in and of themselves; they are generic, all-purpose transport containers for moving both voice and data. The basic format of

3116-439: The benefits have been debated. The Nyquist–Shannon sampling theorem shows PCM devices can operate without introducing distortions within their designed frequency bands if they provide a sampling frequency at least twice that of the highest frequency contained in the input signal. For example, in telephony , the usable voice frequency band ranges from approximately 300  Hz to 3400 Hz. For effective reconstruction of

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3192-445: The channel. In other cases, extra framing bits are added into the stream, which guarantees at least occasional symbol transitions. Another technique used to control ones-density is the use of a scrambler on the data, which will tend to turn the data stream into a stream that looks pseudo-random , but where the data can be recovered exactly by a complementary descrambler. In this case, long runs of zeroes or ones are still possible on

3268-511: The company acquired Atrato IP Networks, a provider of IP and transit services. In 2014 Hibernia, together with TE SubCom, a TE Connectivity Ltd. company, announced the commencement of the new 4,600 km submarine cable system that will provide the lowest-latency fiber-optic path between New York and London. In June, 2016 the two companies received the GTB Innovation Award for Fixed Infrastructure. On January 9, 2017, Hibernia

3344-539: The diagram, a sine wave (red curve) is sampled and quantized for PCM. The sine wave is sampled at regular intervals, shown as vertical lines. For each sample, one of the available values (on the y-axis) is chosen. The PCM process is commonly implemented on a single integrated circuit called an analog-to-digital converter (ADC). This produces a fully discrete representation of the input signal (blue points) that can be easily encoded as digital data for storage or manipulation. Several PCM streams could also be multiplexed into

3420-419: The digital domain. These simple techniques have been largely rendered obsolete by modern transform-based audio compression techniques, such as modified discrete cosine transform (MDCT) coding. In telephony, a standard audio signal for a single phone call is encoded as 8,000 samples per second , of 8 bits each, giving a 64 kbit/s digital signal known as DS0 . The default signal compression encoding on

3496-556: The first commercial digital recordings. In 1972, Denon unveiled the first 8-channel digital recorder, the DN-023R, which used a 4-head open reel broadcast video tape recorder to record in 47.25 kHz, 13-bit PCM audio. In 1977, Denon developed the portable PCM recording system, the DN-034R. Like the DN-023R, it recorded 8 channels at 47.25 kHz, but it used 14-bits "with emphasis , making it equivalent to 15.5 bits." In 1979,

3572-437: The first digital pop album, Bop till You Drop , was recorded. It was recorded in 50 kHz, 16-bit linear PCM using a 3M digital tape recorder. The compact disc (CD) brought PCM to consumer audio applications with its introduction in 1982. The CD uses a 44,100 Hz sampling frequency and 16-bit resolution and stores up to 80 minutes of stereo audio per disc. The rapid development and wide adoption of PCM digital telephony

3648-448: The first layer in the OSI networking model. The ATM and SDH layers are the regenerator section level, digital line level, transmission path level, virtual path level, and virtual channel level. The physical layer is modeled on three major entities: transmission path, digital line and the regenerator section. The regenerator section refers to the section and photonic layers. The photonic layer

3724-575: The frame graphically: as a block of 90 columns and nine rows for STS-1, and 270 columns and nine rows for STM1/STS-3c. This representation aligns all the overhead columns, so the overhead appears as a contiguous block, as does the payload. The internal structure of the overhead and payload within the frame differs slightly between SONET and SDH, and different terms are used in the standards to describe these structures. Their standards are extremely similar in implementation, making it easy to interoperate between SDH and SONET at any given bandwidth. In practice,

3800-515: The functionality of regenerators has been absorbed by the transponders of wavelength-division multiplexing systems. STS multiplexer and demultiplexer provide the interface between an electrical tributary network and the optical network. Add-drop multiplexers (ADMs) are the most common type of network elements. Traditional ADMs were designed to support one of the network architectures, though new generation systems can often support several architectures, sometimes simultaneously. ADMs traditionally have

3876-416: The information payload. Thus, an OC-3 circuit can carry 150.336 Mbit/s of payload, after accounting for the overhead. Carried within the information payload, which has its own frame structure of nine rows and 261 columns, are administrative units identified by pointers. Also within the administrative unit are one or more virtual containers (VCs). VCs contain path overhead and VC payload. The first column

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3952-473: The internal complex structure previously used to transport circuit-oriented connections was removed and replaced with a large and concatenated frame (such as STS-3c) into which ATM cells, IP packets, or Ethernet frames are placed. Both SDH and SONET are widely used today: SONET in the United States and Canada , and SDH in the rest of the world. Although the SONET standards were developed before SDH, it

4028-449: The late 1940s and early 1950s used a cathode-ray coding tube with a plate electrode having encoding perforations. As in an oscilloscope , the beam was swept horizontally at the sample rate while the vertical deflection was controlled by the input analog signal, causing the beam to pass through higher or lower portions of the perforated plate. The plate collected or passed the beam, producing current variations in binary code, one bit at

4104-461: The network commands and underlying (data) protocols. With advances in SONET and SDH chipsets, the traditional categories of network elements are no longer distinct. Nevertheless, as network architectures have remained relatively constant, even newer equipment (including multi-service provisioning platforms ) can be examined in light of the architectures they will support. Thus, there is value in viewing new, as well as traditional, equipment in terms of

4180-439: The older categories. Traditional regenerators terminate the section overhead, but not the line or path. Regenerators extend long-haul routes in a way similar to most regenerators, by converting an optical signal that has already traveled a long distance into electrical format and then retransmitting a regenerated high-power signal. Since the late 1990s, regenerators have been largely replaced by optical amplifiers . Also, some of

4256-521: The output but are considered unlikely enough to allow reliable synchronization. In other cases, the long term DC value of the modulated signal is important, as building up a DC bias will tend to move communications circuits out of their operating range. In this case, special measures are taken to keep a count of the cumulative DC bias and to modify the codes if necessary to make the DC bias always tend back to zero. Many of these codes are bipolar codes , where

4332-488: The overall framing, as the data is clocked at a different rate than the frame rate. The protocol is made more complex by the decision to permit this padding at most levels of the multiplexing structure, but it improves all-around performance. The basic unit of framing in SDH is a STM-1 (Synchronous Transport Module, level 1), which operates at 155.520 megabits per second (Mbit/s). SONET refers to this basic unit as an STS-3c (Synchronous Transport Signal 3, concatenated). When

4408-638: The path layer. It provides synchronization and multiplexing for multiple paths. It modifies overhead bits relating to quality control. The path layer is SONET's highest level layer. It takes data to be transmitted and transforms them into signals required by the line layer, and adds or modifies the path overhead bits for performance monitoring and protection switching. Network management systems are used to configure and monitor SDH and SONET equipment either locally or remotely. The systems consist of three essential parts, covered later in more detail: The main functions of network management thereby include: Consider

4484-622: The payload bandwidth, but path-overhead bandwidth is variable based on the types of cross-connects built across the optical system. Note that the data-rate progression starts at 155 Mbit/s and increases by multiples of four. The only exception is OC-24, which is standardized in ANSI T1.105, but not a SDH standard rate in ITU-T G.707. Other rates, such as OC-9, OC-18, OC-36, OC-96, and OC-1536, are defined but not commonly deployed; most are considered orphaned rates. The physical layer refers to

4560-540: The pulses can be positive, negative or absent. In the typical alternate mark inversion code, non-zero pulses alternate between being positive and negative. These rules may be violated to generate special symbols used for framing or other special purposes. The word pulse in the term pulse-code modulation refers to the pulses to be found in the transmission line. This perhaps is a natural consequence of this technique having evolved alongside two analog methods, pulse-width modulation and pulse-position modulation , in which

4636-514: The same title was filed by John R. Pierce in 1945, and issued in 1948: U.S. patent 2,437,707 . The three of them published "The Philosophy of PCM" in 1948. The T-carrier system, introduced in 1961, uses two twisted-pair transmission lines to carry 24 PCM telephone calls sampled at 8 kHz and 8-bit resolution. This development improved capacity and call quality compared to the previous frequency-division multiplexing schemes. In 1973, adaptive differential pulse-code modulation (ADPCM)

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4712-450: The terms STS-1 and OC-1 are sometimes used interchangeably, though the OC designation refers to the signal in its optical form. It is therefore incorrect to say that an OC-3 contains 3 OC-1s: an OC-3 can be said to contain 3 STS-1s. The Synchronous Transport Module, level 1 (STM-1) frame is the basic transmission format for SDH—the first level of the synchronous digital hierarchy. The STM-1 frame

4788-515: The three parts defined above: This will often consist of software running on a Workstation covering a number of SDH/SONET network elements SONET equipment is often managed with the TL1 protocol. TL1 is a telecom language for managing and reconfiguring SONET network elements. The command language used by a SONET network element, such as TL1, must be carried by other management protocols, such as SNMP , CORBA , or XML . SDH has been mainly managed using

4864-478: The trading community low-latency routes to financial exchanges and data centers. On September 30, 2010, Hibernia announced plans for a new transatlantic cable, Project Express, to be built from the NY metro area to the town of Slough, west of London, with less than 60 ms of delay. This cable system targeted traders and was planned to be the highest bit rate (8.8 terabits/second), lowest latency (59 ms) cable built across

4940-406: The transmission system itself, which is used for a wide range of management functions, such as monitoring transmission quality, detecting failures, managing alarms, data communication channels, service channels, etc. The STM frame is continuous and is transmitted in a serial fashion: byte-by-byte, row-by-row. The transport overhead is used for signaling and measuring transmission error rates , and

5016-585: The use of PCM for voice communication in 1937 while working for International Telephone and Telegraph in France. He described the theory and its advantages, but no practical application resulted. Reeves filed for a French patent in 1938, and his US patent was granted in 1943. By this time Reeves had started working at the Telecommunications Research Establishment . The first transmission of speech by digital techniques,

5092-692: The voice signal even further. An ADPCM algorithm is used to map a series of 8-bit μ-law or A-law PCM samples into a series of 4-bit ADPCM samples. In this way, the capacity of the line is doubled. The technique is detailed in the G.726 standard. Audio coding formats and audio codecs have been developed to achieve further compression. Some of these techniques have been standardized and patented. Advanced compression techniques, such as modified discrete cosine transform (MDCT) and linear predictive coding (LPC), are now widely used in mobile phones , voice over IP (VoIP) and streaming media . PCM can be either return-to-zero (RZ) or non-return-to-zero (NRZ). For

5168-452: The voice signal, telephony applications therefore typically use an 8000 Hz sampling frequency which is more than twice the highest usable voice frequency. Regardless, there are potential sources of impairment implicit in any PCM system: Some forms of PCM combine signal processing with coding. Older versions of these systems applied the processing in the analog domain as part of the analog-to-digital process; newer implementations do so in

5244-523: The world. The company operated in European and North American markets and transported content across its optical switching and dynamic transport mode network. On September 18, 2012 Hibernia announced it was contracted by global infrastructure provider Voxility to provide European and transatlantic capacity between the company's data centers in North America, United Kingdom and Germany. In 2013,

5320-795: Was acquired for $ 607 million (initial price was $ 590 million) by telecommunications provider GTT Communications, Inc. Download coordinates as: Hibernia's network had cable landing stations in: An additional landing point was established in Coleraine , County Londonderry (under Project Kelvin), Northern Ireland, United Kingdom. SONET Synchronous Optical Networking ( SONET ) and Synchronous Digital Hierarchy ( SDH ) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At low transmission rates data can also be transferred via an electrical interface. The method

5396-524: Was defined by Telcordia and American National Standards Institute (ANSI) standard T1.105. which define the set of transmission formats and transmission rates in the range above 51.840 Mbit/s. SDH differs from Plesiochronous Digital Hierarchy (PDH) in that the exact rates that are used to transport the data on SONET/SDH are tightly synchronized across the entire network, using atomic clocks . This synchronization system allows entire inter-country networks to operate synchronously, greatly reducing

5472-605: Was developed to replace the plesiochronous digital hierarchy (PDH) system for transporting large amounts of telephone calls and data traffic over the same fiber without the problems of synchronization. SONET and SDH, which are essentially the same, were originally designed to transport circuit mode communications (e.g., DS1 , DS3 ) from a variety of different sources, but they were primarily designed to support real-time, uncompressed, circuit-switched voice encoded in PCM format. The primary difficulty in doing this prior to SONET/SDH

5548-564: Was developed, by P. Cummiskey, Nikil Jayant and James L. Flanagan . In 1967, the first PCM recorder was developed by NHK 's research facilities in Japan. The 30 kHz 12-bit device used a compander (similar to DBX Noise Reduction ) to extend the dynamic range, and stored the signals on a video tape recorder . In 1969, NHK expanded the system's capabilities to 2-channel stereo and 32 kHz 13-bit resolution. In January 1971, using NHK's PCM recording system, engineers at Denon recorded

5624-438: Was enabled by metal–oxide–semiconductor (MOS) switched capacitor (SC) circuit technology, developed in the early 1970s. This led to the development of PCM codec-filter chips in the late 1970s. The silicon-gate CMOS (complementary MOS) PCM codec-filter chip, developed by David A. Hodges and W.C. Black in 1980, has since been the industry standard for digital telephony. By the 1990s, telecommunication networks such as

5700-577: Was originally built in 2000 by Tyco Submarine Systems for 360networks for $ 962M. It was placed in receivership in 2001, purchased in 2003 and began carrying traffic in 2005. In 2007 Hibernia announced that Huawei Technologies USA had been selected to upgrade Hibernia's 24,520 kilometers of the submarine and terrestrial network throughout the US, Canada, the UK, and Europe. In December 2009, Hibernia Networks acquired managed network services company MediaXstream. Hibernia Networks provided financial customers and

5776-408: Was that the synchronization sources of these various circuits were different. This meant that each circuit was actually operating at a slightly different rate and with different phase. SONET/SDH allowed for the simultaneous transport of many different circuits of differing origin within a single framing protocol. SONET/SDH is not a complete communications protocol in itself, but a transport protocol (not

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