This invention relates to an optical transmission system including an additional optical service channel for system management.
Optical transmission systems often use an optical service channel to communicate status and control information between various transceivers, amplifiers and transponders in an optical transmission system. It is important to minimize the insertion loss of the wavelength multiplexing filter used to couple the optical channels used to transmit payload data such as wave division multiplex (WDM) channels and the optical service channel (OSC).
Several prior art approaches exist, but none have the features of the current invention. For instance, U.S. Pat. No. 6,327,060 to Otani discloses an optical transmission system having an add drop station controlled by four optical circulators which allows signals to be added and dropped via fiber gratings which reflect selective wavelengths. The invention accomplishes a bypass of an optical supervisory channel but does not provide for the insertion and removal of an optical supervisory channel by optical circulators. Otani also suffers from adding additional unnecessary optical components which increase optical losses.
Another example is U.S. Pat. No. 6,122,095 to Fitehi. This patent discloses an optical add/drop multiplexor using one or more fiber gratings which are disposed along the length of rare earth doped fiber or between segments for reflecting optical signals which are added or dropped through circulators. However, Fitehi does not provide for a separate counter propagating optical service channel.
Another example is U.S. Pat. No. 5,299,048 to Suyama. This patent provides an optical communication system which employed a dichromic separator to distinguish between a signal light and a pumping light where the pumping light carries control information. However, Suyama suffers from the addition of losses in the dichromic separator and other losses associated with the addition of other optical components.
Therefore, a need exists for an optical transmission system which has an additional optical service channel for system management which has minimal impact on the WDM channels in the area of insertion loss.
The invention provides for optical circulators which redirect light from port to port sequentially in one direction used to separate traffic in a bidirectional optical fiber transmission system. The invention provides for using two optical circulators in each span of bidirectional fiber so that the OSC channel can be transmitted in one direction opposite to the WDM channels. The optical circulator is a low loss device which additionally has the attribute of uniform loss or very large optical bandwidth. Therefore, the invention provides the advantage of using a wide band circulator which does not impose a pass band shape on the WDM channel and therefore does not display accumulation of filter loss over long system spans. Additionally, the invention provides the advantage of a large tolerance on the optical service channel which allows uncooled distributed feedback or distributed bragg reflectors (DFB) lasers to be used which reduces system costs.
The invention also provides for a gigabit ethernet path between chassis which is utilized for control traffic and customer traffic. The invention is placed in a non-critical region of the optical spectrum and is independent of all other chassis equipment.
The invention also provides the advantage in alternate embodiments of providing the option of a second counter propagating WDM channel being transmitted along with the OSC to provide additional system capacity. The invention also provides the advantage in an alternate embodiment of allowing the OSC to be amplified through a raman source without the need of complete system retrofit.
Referring to
In operation, in the A-Z direction, an optical signal in the L band range of 1570-1610 nm is sent to optical amplifier 145 and immediately transmitted to port 125c of circulator 125. The signal passes to port 125b of circulator 125 for transmission along optical fiber 165 to port 120b of optical circulator 120. The signal is passed to port 120c and on to optical amplifier 140. Management card 155 provides a counter propagating optical service channel at 1510 nm, 1540 nm or 1625 nm along optical fiber 185 to port 120a of optical circulator 120. In the preferred embodiment, management card 155 produces the OSC with an uncooled DFB laser which may be used despite its wavelength variation of 12 nm over a 700 temperature change because of the configuration of circulators 120 and 125. OSC is passed to port 120b of optical circulator 120 and then is counter propagated in the direction 190 to port 125b of optical circulator 125. The OSC is then passed to port 125a of optical circulator 125 along optical fiber 175 to management card 150 to be decoded and used to operate or check the status of the optical transmission system. In the preferred embodiment, management cards 150 and 155 include full duplex optical transceivers.
In the Z-A direction an L band signal is provided to optical amplifier 135 which is passed to port 115b of circulator 115, then on to exit at port 115c through optical fiber 160 to port 110b of the optical circulator 110. The signal then exits optical circulator 110 at port 110c to be amplified by amplifier 130 before moving on to the next amplifier or receiver in the optical transmission system. Management card 150 creates an OSC which is transmitted along fiber 170 to port 110a of circulator 110 at 1510 nm, 1540 nm or 1625 nm. Of course other frequencies are possible. The signal exits circulator 110 at port 110b and onto optical fiber 160 in the direction 165 where it enters optical circulator 115 at port 115c and exits at port 115a. After exiting 115a the counter propagating OSC travels through fiber 180 to management card 155 where the control information passed is used to control or check the status of the optical transmission system.
In the preferred embodiment, the format of the OSC is a separate wavelength which is independent of and transparent to the other wavelengths being transmitted on the system. The OSC in the preferred embodiment is a full duplex gigabit Ethernet signal which also can be utilized for customer traffic. The OSC provides for generic customer LAN connectivity at all sites. It enables any customer access to the LAN that can run on an Ethernet network. The gigabit Ethernet OSC also provides high bandwidth for control traffic between terminal sites.
An alternate embodiment of the preferred invention is shown at
One advantage of the transmission system shown in
The second WDM transmission band and the OSC can be separated at the optical amplifiers with conventional wavelength multiplexing filters. The second WDM transmission band can be used to implement a shortened optical path which can contain ultra long haul channels and additional metro channels on the same fiber.
Optical amplifiers 302, 303, 304 and 305 operate similarly to that described with respect to
A further alternate embodiment is shown in
Optical amplifiers 397, 398, 399 and 400 perform similar functions to those described with respect to
The advantage of this preferred embodiment is that the previously installed optical circulators can be used to add distributed raman amplification to the system without disturbing the WDM signal traffic. In this embodiment the circulators must have sufficient power ratings for a raman pump laser source in the 500 mW range. Additionally, wavelength multiplexors 310 and 320 are necessary to couple the OSC and the raman pump wavelengths.
The previous descriptions are of preferred examples for implementing the invention, and the scope of the invention should not necessarily be limited by this description. The scope of the present invention is defined by the following claims:
This application claims priority to Provisional Application Ser. No. 60/377,159, entitled “Wave Division Multiplexed Optical Transport System Utilizing Optical Circulators to Isolate an Optical Service Channel”, by Eiselt, et al., filed Apr. 30, 2002, and Provisional Application Ser. No. 60/376,978, entitled “Method and Architecture for Utilizing Gigabit Ethernet as an Optical Supervisory Channel”, by Jeffrey Lloyd Cox, filed Apr. 30, 2002.
Number | Name | Date | Kind |
---|---|---|---|
4229831 | Lacher | Oct 1980 | A |
4535459 | Hogge, Jr. | Aug 1985 | A |
4636859 | Vernhet et al. | Jan 1987 | A |
4710022 | Soeda et al. | Dec 1987 | A |
5224183 | Dugan | Jun 1993 | A |
5225922 | Chraplyvy et al. | Jul 1993 | A |
5267071 | Little et al. | Nov 1993 | A |
5299048 | Suyama | Mar 1994 | A |
5321541 | Cohen | Jun 1994 | A |
5455703 | Duncan et al. | Oct 1995 | A |
5559625 | Smith et al. | Sep 1996 | A |
5613210 | Van Driel et al. | Mar 1997 | A |
5712932 | Alexander et al. | Jan 1998 | A |
5726784 | Alexander et al. | Mar 1998 | A |
5737118 | Sugaya et al. | Apr 1998 | A |
5778116 | Tomich | Jul 1998 | A |
5790285 | Mock | Aug 1998 | A |
5812290 | Maeno et al. | Sep 1998 | A |
5877881 | Miyauchi et al. | Mar 1999 | A |
5903613 | Ishida | May 1999 | A |
5914794 | Fee | Jun 1999 | A |
5914799 | Tan | Jun 1999 | A |
5936753 | Ishikaawa | Aug 1999 | A |
5940209 | Nguyen | Aug 1999 | A |
5963350 | Hill | Oct 1999 | A |
5995694 | Akasaka et al. | Nov 1999 | A |
6005702 | Suzuki et al. | Dec 1999 | A |
6021245 | Berger et al. | Feb 2000 | A |
6038062 | Kosaka | Mar 2000 | A |
6075634 | Casper et al. | Jun 2000 | A |
6078414 | Iwano | Jun 2000 | A |
6081360 | Ishikawa et al. | Jun 2000 | A |
6084694 | Milton et al. | Jul 2000 | A |
6088152 | Berger et al. | Jul 2000 | A |
6108074 | Bloom | Aug 2000 | A |
6122095 | Fatehi | Sep 2000 | A |
6151334 | Kim et al. | Nov 2000 | A |
6157477 | Robinson | Dec 2000 | A |
6160614 | Unno | Dec 2000 | A |
6163392 | Condict et al. | Dec 2000 | A |
6163636 | Stentz et al. | Dec 2000 | A |
6173094 | Bowerman et al. | Jan 2001 | B1 |
6177985 | Bloom | Jan 2001 | B1 |
6198559 | Gehlot | Mar 2001 | B1 |
6229599 | Galtarossa | May 2001 | B1 |
6236481 | Laor | May 2001 | B1 |
6236499 | Berg et al. | May 2001 | B1 |
6246510 | BuAbbud et al. | Jun 2001 | B1 |
6259553 | Kinoshita | Jul 2001 | B1 |
6259554 | Shigematsu et al. | Jul 2001 | B1 |
6259693 | Ganmukhi et al. | Jul 2001 | B1 |
6259845 | Sardesai | Jul 2001 | B1 |
6272185 | Brown | Aug 2001 | B1 |
6275315 | Park et al. | Aug 2001 | B1 |
6278536 | Kai et al. | Aug 2001 | B1 |
6288811 | Jiang et al. | Sep 2001 | B1 |
6288813 | Kirkpatrick et al. | Sep 2001 | B1 |
6292289 | Sugaya et al. | Sep 2001 | B1 |
6307656 | Terahara | Oct 2001 | B2 |
6317231 | Al-Salameh et al. | Nov 2001 | B1 |
6317255 | Fatehi et al. | Nov 2001 | B1 |
6323950 | Kim et al. | Nov 2001 | B1 |
6327060 | Otani et al. | Dec 2001 | B1 |
6356384 | Islam | Mar 2002 | B1 |
6359729 | Amoruso | Mar 2002 | B1 |
6388801 | Sugaya et al. | May 2002 | B1 |
6396853 | Humphrey et al. | May 2002 | B1 |
6414769 | Meli et al. | Jul 2002 | B1 |
6433903 | Barry et al. | Aug 2002 | B1 |
6519082 | Ghera et al. | Feb 2003 | B2 |
6532320 | Kikuchi et al. | Mar 2003 | B1 |
6775055 | Tsuzaki et al. | Aug 2004 | B2 |
6930823 | Nakamoto et al. | Aug 2005 | B2 |
20010005271 | Leclerc et al. | Jun 2001 | A1 |
20010007605 | Inagaki et al. | Jul 2001 | A1 |
20010009468 | Fee | Jul 2001 | A1 |
20010014104 | Bottorff et al. | Aug 2001 | A1 |
20010021044 | Lim | Sep 2001 | A1 |
20020012152 | Agazzi et al. | Jan 2002 | A1 |
20020015220 | Papernyl et al. | Feb 2002 | A1 |
20020034197 | Tornetta et al. | Mar 2002 | A1 |
20020044317 | Gentner et al. | Apr 2002 | A1 |
20020044324 | Hoshida et al. | Apr 2002 | A1 |
20020048287 | Silvers | Apr 2002 | A1 |
20020051468 | Ofek et al. | May 2002 | A1 |
20020063948 | Islam et al. | May 2002 | A1 |
20020064181 | Ofek et al. | May 2002 | A1 |
20020075903 | Hind | Jun 2002 | A1 |
20020080809 | Nicholson et al. | Jun 2002 | A1 |
20030151802 | Berg et al. | Aug 2003 | A1 |
Number | Date | Country |
---|---|---|
01115230 | May 1989 | JP |
02238736 | Sep 1990 | JP |
Number | Date | Country | |
---|---|---|---|
20040033080 A1 | Feb 2004 | US |
Number | Date | Country | |
---|---|---|---|
60377159 | Apr 2002 | US | |
60376978 | Apr 2002 | US |