TOSLINK
Encyclopedia
TOSLINK is a standardized optical fiber
connection
system. Also known generically as an "optical audio cable," its most common use is in consumer audio equipment (via a "digital optical" socket), where it carries a digital audio
stream from components such as MiniDisc
, CD
and DVD
players, DAT
recorders, computers, and modern video game console
s, to an AV receiver
that can decode the stream of audio and output it through a set of loudspeaker
s. Although TOSLINK supports several different media formats and physical standards, digital audio connections using the rectangular EIAJ/JEITA
RC-5720 (also CP-1201 and JIS C5974-1993 F05) connector are by far the most common. The optical signal is a red light, with a peak wavelength λ of 650 nm. Depending on the type of modulated signal
being carried, other optical wavelengths may be present.
Toshiba
originally created TOSLINK to connect their CD players to the receivers they manufactured for PCM audio streams. It was soon adopted by manufacturers of most CD players. Early TOSLINK systems used the raw PCM data from the CD player; the S/PDIF
standard has now become nearly universal for audio streams. It can often be found on DVD players and some game consoles to connect the digital audio stream to Dolby Digital
/DTS decoders.
The name is a registered trademark
of Toshiba, created from TOShiba-LINK. Variations of the name, such as TOSlink, TosLink, and Tos-link, are also seen, while the official generic name for the standard is EIAJ optical.
Other terms are sometimes used for technology similar to TOSLINK, such as ADAT Lightpipe
or simply ADAT Optical. These are most often seen in the professional music/audio industry. While the ADAT Lightpipe format uses the same JIS F05 connectors as TOSLINK, the ADAT Lightpipe data format is not compatible with S/PDIF
.
, TOSLINK cables are widely rumored to introduce jitter
(reproduction inaccuracies due to timing errors), erroneously described as "smearing" or a poorly articulated sound. However, the actual effect of jitter on audio reproduction is an increase in noise
or intermodulation
, and most humans' hearing is not likely to notice any effect. Multi-strand glass fiber TOSLINK cables might cause less jitter than larger diameter, single strand cables. (See Jitter.) One cause of jitter is bandwidth-limiting of the digital signal.
TOSLINK cables can temporarily fail or be permanently damaged if tightly bent. Their high light-signal attenuation limits their effective range to about 6 metres (19.7 ft).
Optical cables are not susceptible to electrical problems such as ground loops
and RF interference.
Bandwidth
can be 10 MHz with high-purity quartz fiber, but 5 to 6 MHz for a cheaper plastic cable.
Several types of fiber can be used for TOSLINK: inexpensive 1 mm plastic optical fiber, higher-quality multistrand plastic optical fibers, or quartz glass optical fibers, depending on the desired bandwidth and application. TOSLINK cables are usually limited to 5 meters in length, with a technical maximum of 10 meters, for reliable transmission without the use of a signal booster or a repeater. However, it is very common for interfaces on newer consumer electronics (satellite receivers and PCs with optical outputs) to easily run over 30 meters on even low-cost ($0.75/m) TOSLINK cables. TOSLINK transmitters operate at a nominal optical wavelength of 650 nm(~461.2 THz).
Mini-TOSLINK is a standardized optical fiber
connector
smaller than the standard square TOSLINK connector commonly used in larger consumer audio equipment.
The plug is almost exactly the same size and shape as the ubiquitous 3.5 mm stereo minijack
. Adapters are available to connect a full-size TOSLINK plug to a mini-TOSLINK socket. There are combined 3.5 mm jack and mini-TOSLINK sockets which can accept a 3.5 mm jack or a mini-TOSLINK plug; mini-TOSLINK plugs are made 0.5mm longer than electrical jack plugs so that the latter are too short to touch and damage the LED of combined connectors. Many notebook computers use these connectors, e.g. for 3.5 mm electrical headphone output combined with TOSLINK digital output (not both at the same time), and for electrical microphone and TOSLINK line-in. Mini-TOSLINK jacks are commonly used on Apple computers and portable digital audio equipment.
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
connection
Optical fiber connector
An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so that light can pass...
system. Also known generically as an "optical audio cable," its most common use is in consumer audio equipment (via a "digital optical" socket), where it carries a digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
stream from components such as MiniDisc
MiniDisc
The disc is permanently housed in a cartridge with a sliding door, similar to the casing of a 3.5" floppy disk. This shutter is opened automatically by a mechanism upon insertion. The audio discs can either be recordable or premastered. Recordable MiniDiscs use a magneto-optical system to record...
, CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
and DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
players, DAT
Digital Audio Tape
Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As...
recorders, computers, and modern video game console
Video game console
A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
s, to an AV receiver
AV receiver
AV receivers or audio-video receivers are one of the many consumer electronics components typically found within a home theatre system. Their primary purpose is to amplify sound from a multitude of possible audio sources as well as route video signals to your TV from various sources. The user may...
that can decode the stream of audio and output it through a set of loudspeaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s. Although TOSLINK supports several different media formats and physical standards, digital audio connections using the rectangular EIAJ/JEITA
Jeita
Jeita is a Lebanese town located in the Keserwan District in the Mount Lebanon Governorate. The town is about north of Beirut. It is famous for the Jeita Grotto which is a popular tourist attraction, as well as the Nahr al-Kalb, a river that runs from a spring near the grotto emptying into the...
RC-5720 (also CP-1201 and JIS C5974-1993 F05) connector are by far the most common. The optical signal is a red light, with a peak wavelength λ of 650 nm. Depending on the type of modulated signal
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
being carried, other optical wavelengths may be present.
History
Toshiba
is a multinational electronics and electrical equipment corporation headquartered in Tokyo, Japan. It is a diversified manufacturer and marketer of electrical products, spanning information & communications equipment and systems, Internet-based solutions and services, electronic components and...
originally created TOSLINK to connect their CD players to the receivers they manufactured for PCM audio streams. It was soon adopted by manufacturers of most CD players. Early TOSLINK systems used the raw PCM data from the CD player; the S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
standard has now become nearly universal for audio streams. It can often be found on DVD players and some game consoles to connect the digital audio stream to Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
/DTS decoders.
The name is a registered trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
of Toshiba, created from TOShiba-LINK. Variations of the name, such as TOSlink, TosLink, and Tos-link, are also seen, while the official generic name for the standard is EIAJ optical.
Other terms are sometimes used for technology similar to TOSLINK, such as ADAT Lightpipe
ADAT Lightpipe
The ADAT Lightpipe, officially the ADAT Optical Interface, is a standard for the transfer of digital audio between equipment. It was originally developed by Alesis but has since become widely accepted, with many third party hardware manufacturers including Lightpipe interfaces on their equipment...
or simply ADAT Optical. These are most often seen in the professional music/audio industry. While the ADAT Lightpipe format uses the same JIS F05 connectors as TOSLINK, the ADAT Lightpipe data format is not compatible with S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
.
Properties and issues
Due to the use of clock recoveryClock recovery
Some digital data streams, especially high-speed serial data streams are sent without an accompanying clock signal. The receiver generates a clock from an approximate frequency reference, and then phase-aligns to the transitions in the data stream with a phase-locked loop...
, TOSLINK cables are widely rumored to introduce jitter
Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of...
(reproduction inaccuracies due to timing errors), erroneously described as "smearing" or a poorly articulated sound. However, the actual effect of jitter on audio reproduction is an increase in noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
or intermodulation
Intermodulation
Intermodulation or intermodulation distortion is the amplitude modulation of signals containing two or more different frequencies in a system with nonlinearities...
, and most humans' hearing is not likely to notice any effect. Multi-strand glass fiber TOSLINK cables might cause less jitter than larger diameter, single strand cables. (See Jitter.) One cause of jitter is bandwidth-limiting of the digital signal.
TOSLINK cables can temporarily fail or be permanently damaged if tightly bent. Their high light-signal attenuation limits their effective range to about 6 metres (19.7 ft).
Optical cables are not susceptible to electrical problems such as ground loops
Ground loop (electricity)
In an electrical system, a ground loop usually refers to a current, almost always unwanted, in a conductor connecting two points that are supposed to be at the same potential, often ground, but are actually at different potentials. Ground loops created by improperly designed or improperly installed...
and RF interference.
Bandwidth
Bandwidth
Bandwidth is the difference between the upper and lower frequencies in a contiguous set of frequencies. It is typically measured in hertz, and may sometimes refer to passband bandwidth, sometimes to baseband bandwidth, depending on context...
can be 10 MHz with high-purity quartz fiber, but 5 to 6 MHz for a cheaper plastic cable.
Design
Mini-TOSLINK
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
connector
Optical fiber connector
An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so that light can pass...
smaller than the standard square TOSLINK connector commonly used in larger consumer audio equipment.
The plug is almost exactly the same size and shape as the ubiquitous 3.5 mm stereo minijack
TRS connector
A TRS connector is a common family of connector typically used for analog signals including audio. It is cylindrical in shape, typically with three contacts, although sometimes with two or four . It is also called an audio jack, phone jack, phone plug, and jack plug...
. Adapters are available to connect a full-size TOSLINK plug to a mini-TOSLINK socket. There are combined 3.5 mm jack and mini-TOSLINK sockets which can accept a 3.5 mm jack or a mini-TOSLINK plug; mini-TOSLINK plugs are made 0.5mm longer than electrical jack plugs so that the latter are too short to touch and damage the LED of combined connectors. Many notebook computers use these connectors, e.g. for 3.5 mm electrical headphone output combined with TOSLINK digital output (not both at the same time), and for electrical microphone and TOSLINK line-in. Mini-TOSLINK jacks are commonly used on Apple computers and portable digital audio equipment.