Laser drivers for closed path optical cables

• US 8,233,805 B2
• Filed: 12/27/2010
• Issued: 07/31/2012
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Finisar Corporation (II-VI Incorporated)
• Inventors: Tatum, Jimmy A., Guenter, James K.
• Primary Examiner(s): Bello, Agustin
• Application Number:
  US12/979,243
• Publication Number:
  US 20110091219A1
• Time in Patent Office: 582 Days
• Field of Search: 398139-141
• US Class Current: 398/141
• CPC Class Codes: G02B 6/4201 Packages, e.g. shape, construction, internal or external details
• CPC Class Codes: G02B 6/4246 Bidirectionally operating package structures
• CPC Class Codes: G09G 2370/12 Use of DVI or HDMI protocol in interfaces along the display data pipeline
• CPC Class Codes: G09G 2370/18 Use of optical transmission of display information
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02 Structural details or components not essential to laser action
• CPC Class Codes: H01S 5/02212 Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis
• CPC Class Codes: H01S 5/0262 Photo-diodes, e.g. transceiver devices, bidirectional devices H01S5/0265 takes precedence
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/18313 by oxidizing at least one of the DBR layers
• CPC Class Codes: H01S 5/3095 Tunnel junction
• CPC Class Codes: H04B 10/801 using optical interconnects, e.g. light coupled isolators, circuit board interconnections
• CPC Class Codes: H04J 14/08 Time-division multiplex systems

Abstract

Simplified laser drivers for closed path digital optical cables and digital optical cables including the simplified laser drivers. The laser driver can include less transistors than conventional laser drivers for optical communication cables. The laser can include a bias source and modulation source. The bias source can have a single constant current bias point for all laser diodes. The modulation current source can have a single temperature coefficient for all laser diodes. The laser driver can exclude, for example, any one of or combination of temperature compensation of the modulation or bias current sources, external programming of the modulation or bias current sources, power control based on output of the laser diode, and/or control based on feedback received from a monitor device or other sensor within the cables.

Claims

1. A closed path digital optical cable comprising:

an optical fiber having a first end and a second end;

a first interface configured to couple the closed path digital optical cable to a digital source device, the first interface comprising;

an optical transmitter configured to receive a first electronic signal from the digital source device and to convert the first electronic signal to one or more optical signals, and transmit the one or more optical signals onto the first end of the optical fiber; and

a laser driver circuit configured to provide a drive current to the optical transmitter without the use of temperature compensation, the laser driver circuit having a single temperature coefficient under all operating temperatures;

a second interface configured to couple the digital optical cable to a digital sink device, the second interface comprising;

an optical receiver configured to receive the one or more optical signals from the second end of the optical fiber, convert the one or more optical signals to a second electronic signal, and transmit the second electronic signal to the digital sink device, wherein the first interface and the second interface are interconnected with the optical fiber so as to form a closed optical path.

2. The closed path digital optical cable of claim 1, wherein the laser driver circuit comprises one or more transistors, the one or more transistors including less than one hundred transistors.

3. The closed path digital optical cable of claim 2, wherein the one or more transistors include less than five transistors.

4. The closed path digital optical cable of claim 1, wherein:

the first electronic signal is one of a first plurality of transition minimized differential signaling (TMDS) signals;

the second electronic signal is one of a second plurality of TMDS signals;

the first interface further comprises a serializer circuit configured to serialize the plurality of TMDS signals into a first electrical serialized signal;

the one or more optical signals include a single optical signal;

the optical transmitter is configured to convert the first electrical serialized signal into the single optical signal and is configured to transmit the single optical signal onto the first end of the optical fiber;

the optical receiver is configured to receive and convert the single optical signal into a second electrical serialized signal; and

the second interface further comprises a deserializer circuit configured to deserialize the second electrical serialized signal into the second plurality of TMDS signals.

5. The closed path digital optical cable of claim 1, wherein

the first electronic signal is one of a first plurality of transition minimized differential signaling (TMDS) signals;

the second electronic signal is one of a second plurality of TMDS signals;

the one or more optical signals comprise a plurality of optical signals of different wavelengths;

the optical transmitter is one of a plurality of optical transmitters included in the first interface;

the plurality of optical transmitters are configured to convert a corresponding one of the first plurality of TMDS signals to a corresponding one of the plurality of optical signals;

the first interface further comprises a wavelength division multiplexer (WDM) configured to receive and multiplex the plurality of optical signals into a multiplexed optical signal and to couple the multiplexed optical signal onto the first end of the optical fiber;

the second interface further comprises a wavelength division demultiplexer configured to receive and demultiplex the multiplexed optical signal from the second end of the optical fiber into the plurality of optical signals;

the optical receiver is one of a plurality of optical receivers included in the second interface;

the plurality of optical receivers are configured to convert a corresponding one of the plurality of optical signals into a corresponding one of the second plurality of TMDS signals.

6. The closed path digital optical cable of claim 1, wherein:

the first interface comprises a time division multiplexer (TDM) configured to multiplex first signals received from the digital source device in time to generate the first electronic signal prior to transmission of the first electronic signal by the optical transmitter; and

the second interface comprises a time division demultiplexer (TDD) configured to demultiplex the second electronic signal in time to generate second signals provided to the digital sink device.

7. The closed path digital optical cable of claim 1, further comprising an electrical cable having a first end coupled to the first interface and a second end coupled to the second interface, wherein the electrical cable is configured to provide electrical communication for a return signal from the digital sink device to the digital source device.

8. The closed path digital optical cable of claim 1, wherein:

the digital source device comprises a consumer electronic device, including at least one of a DVD player, a digital cable box, or a computer; and

the digital sink device comprises a consumer electronic device, including at least one of a digital television, a digital audio system, or a digital monitor.

9. A method, comprising:

providing a laser driver circuit in a first interface of closed path digital optical cable with a bias current source having a single bias current point and with a modulation current source having a single temperature coefficient under all operating temperatures;

driving, using the laser driver circuit, an optical transmitter included in the first interface to emit an optical signal representing a first electronic signal received from a digital source device coupled to the first interface without the use of temperature compensation;

emitting the optical signal onto an optical fiber coupled between the first interface and a second interface of the closed path digital optical cable;

receiving and converting the optical signal to a second electronic signal using an optical receiver included in the second interface; and

providing data included in the second electronic signal to a digital sink device coupled to the second interface.

10. The method of claim 9, further comprising:

receiving a first plurality of transition minimized differential signaling (TMDS) signals from the digital source device;

serializing the first plurality of TMDS signals into the first electronic signal prior to driving the optical transmitter to emit the optical signal representing the first electronic signal;

deserializing the second electronic signal into a second plurality of TMDS signals after receiving and converting the optical signal to the second electronic signal,

wherein providing data included in the second electronic signal to the digital sink device comprises providing the second plurality of TMDS signals to the digital sink device.

11. The method of claim 9, wherein the first electronic signal is one of a first plurality of transition minimized differential signaling (TMDS) signals and the second electronic signal is one of a second plurality of TMDS signals, the method further comprising:

receiving, at the first interface, the first plurality of TMDS signals from the digital source device;

driving a plurality of optical transmitters included in the first interface to emit a plurality of optical signals representing the first plurality of TMDS signals;

wavelength division multiplexing the plurality of optical signals into a multiplexed optical signal;

coupling the multiplexed optical signal into the optical fiber;

receiving and wavelength division demultiplexing the multiplexed optical signal into the plurality of optical signals at the second interface;

providing the plurality of optical signals to a plurality of optical receivers; and

converting, at the plurality of optical receivers, the plurality of optical signals into the second plurality of TMDS signals,

wherein providing data included in the second electronic signal to the digital sink device comprises providing the second plurality of TMDS signals to the digital sink device.

12. The method of claim 9, further comprising:

receiving a first plurality of transition minimized differential signaling (TMDS) signals from the digital source device;

multiplexing the first TMDS signals in time to generate the first electronic signal; and

demultiplexing the second electronic signal in time to generate a second plurality of TMDS signals,

wherein providing data included in the second electronic signal to the digital sink device comprises providing the second plurality of TMDS signals to the digital sink device.

13. A closed path digital optical cable comprising:

an optical fiber;

a first interface configured to couple the closed path digital optical cable to a digital source device and configure to communicate bidirectionally over the optical fiber, the first interface comprising;

an optical transmitter;

an optical receiver; and

a laser driver circuit comprising a bias current source with only one bias current point and a modulation current source with only one temperature coefficient under all operating temperatures such that the laser driver circuit provides a drive current to the optical transmitter without the use of temperature compensation;

a second interface configured to couple the digital optical cable to a digital sink device and configured to communicate bidirectionally over the optical fiber with the first interface.

14. The closed path digital optical cable of claim 13, wherein the first interface comprises a transceiver, the transceiver comprising:

a transmit optical subassembly (TOSA) including the optical transmitter;

a receive optical subassembly (ROSA) including the optical receiver; and

an optical circulator configured to route outbound optical signals from the TOSA to the optical fiber and configured to route inbound optical signals from the optical fiber to the ROSA.

15. The closed path digital optical cable of claim 13, wherein the first interface comprises a bidirectional multiband optical assembly including the optical transmitter and the optical receiver, the bidirectional multiband optical assembly further comprising:

a wavelength splitter; and

an optical port aligned to communicate optical signals between the optical fiber and the wavelength splitter,

wherein;

the optical transmitter is positioned to emit optical signals along a first optical path to the wavelength splitter;

the optical receiver is positioned to receive optical signals along a second optical path from the wavelength splitter;

the wavelength splitter is configured to reflect optical signals having a first wavelength transmitted along the first optical path from the optical transmitter to the optical port; and

the wavelength splitter is further configured to pass therethrough optical signals having a second wavelength from the optical port to the optical receiver along the second optical path.

16. The closed path digital optical cable of claim 13, wherein:

the optical transmitter and the optical receiver are monolithically integrated in a single semiconductor device, the optical transmitter and the optical receiver being positioned along the same optical axis;

the optical transmitter is configured to emit optical signals having a first wavelength or range of wavelengths;

the optical receiver is configured to absorb optical signals having a second wavelength or range of wavelengths; and

at least one of;

the optical receiver is transparent to optical signals having the first wavelength or range of wavelengths;

or

the optical transmitter is transparent to optical signals having the second wavelength or range of wavelengths.

17. The closed path digital optical cable of claim 16, wherein the optical receiver comprises a plurality of photodiodes formed one on top of another, and wherein a thickness of each of the plurality of photodiodes is such that each of the plurality of photodiodes is configured to absorb approximately the same amount of energy from optical signals having the second wavelength or range of wavelengths.

18. The closed path digital optical cable of claim 17, wherein:

the plurality of photodiodes includes a first photodiode formed above the optical transmitter, a second photodiode formed above the first photodiode, and a third photodiode formed above the second photodiode;

the first photodiode is 0.30 microns thick;

the second photodiode is 0.27 microns thick; and

the third photodiode is 0.23 microns thick.

19. The closed path digital optical cable of claim 16, wherein in a plane normal to an optical axis of the single semiconductor device, the optical receiver has a diameter between about 100 microns and about 200 microns and the optical transmitter has an optical cavity with a diameter between about 5 microns and about 10 microns.

20. The closed path digital optical cable of claim 16, wherein:

the optical transmitter comprises a first p-n junction with a first p-layer and a first n-layer;

the single semiconductor device includes a tunnel junction monolithically coupled to the optical transmitter, the tunnel junction comprising a heavily doped n+ layer and a heavily doped p+ layer;

the optical receiver is monolithically coupled to the tunnel junction, the optical receiver comprising a second p-n junction.