TOSLINK

TOSLINK / EIAJ optical

Clear TOSLINK cable with a round connector.
Type	Optical digital audio connector
Production history
Designer	Toshiba
Designed	1983
Manufacturer	Toshiba
Produced	1983 to present
General specifications
Hot pluggable	Yes
External	Yes
Audio signal	Digital audio bitstream. Originally limited to 48 kHz at 20 bits. Extended to support all modern formats, except Dolby Digital Plus, TrueHD, and DTS HD audio streams.
Cable	Optical Fiber, ~10 m (33 ft) maximum[1]
Pins	1
Connector	JIS F05 (JIS C5974-1993 F05)
Data
Width	32 bit audio packets
Bitrate	Originally 3.1 Mbit/s; Now 125 Mbit/s
Max. devices	1
Protocol	Serial

TOSLINK (from "Toshiba Link"^[2]) is a standardized optical fiber connection system.^[3] 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 consoles, to an AV receiver that can decode the stream of audio and output it through a set of loudspeakers. 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.^[4] The optical signal is a red light, with a peak wavelength λ of 650 nm.^[2] Depending on the type of modulated signal being carried, other optical wavelengths may be present.^[4]

History

TOSLINK connector (JIS F05)

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.

Properties and issues

Due to the use of clock recovery, 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.^{[dubious – discuss]} (See Jitter.) One cause of jitter is bandwidth-limiting of the digital signal.^[5]

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 (20 ft).^[1]

Optical cables are not susceptible to electrical problems such as ground loops and RF interference.^[6]

Bandwidth can be 10 MHz with high-purity quartz fiber, but 5 to 6 MHz for a cheaper plastic cable.^[5]

Design

A TOSLINK fiber optic audio cable being illuminated on one end

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^[1] 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

A mini-TOSLINK adapter

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.

References

1. ^ ^{a b c} epanorama.net. "S/PDIF Interface Document". http://www.epanorama.net/documents/audio/spdif.html. Retrieved 2009-02-16. 
2. ^ ^{a b} Toshiba TOTX1701 TOSLINK Transmitter Module specifications.
3. ^ "What Is TOSLINK?" Toshiba Toslink FAQs.
4. ^ ^{a b} "Product guide, Fiber-Optic Devices TOSLINK(tm)". http://www.digikey.com/Web%20Export/Supplier%20Content/Toshiba_264/PDF/Toshiba_BCE0037_catalog.pdf.  100621 digikey.com
5. ^ ^{a b} Joe Cornwall: TOSLINK Interconnect History & Basics
6. ^ Joseph D. Cornwall (December 31, 2004). "Understanding Digital Interconnects". Audioholics.com. http://www.audioholics.com/education/cables/understanding-digital-interconnects. Retrieved 2007-07-12. 

External links

• TOSLINK Interconnect History & Basics