Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-05-25
2003-05-27
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C375S354000, C375S368000
Reexamination Certificate
active
06570690
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical transmission system, and more particularly to an optical parallel transmission system which converts data of a plurality of bits into an optical signal to transmit the same parallelly.
2. Description of the Related Art
Conventionally, in optical transmission, serial transmission is usually employed so that no skew may occur between bits in long distance transmission, and is used in various fields relating to communications. Since AC coupling which involves determination of presence or absence of data from a variation of data is used in serial transmission, data of successive “0”s cannot be handled. Therefore, in serial transmission, data are transmitted after they are converted into different data having a form close to a repetition of “1” and “0”. For this conversion, coding called 8 B/10 B conversion which converts 8-bit data into 10-bit data is used very frequently.
FIG. 1
is a diagrammatic view showing a conventional serial optical transmission system.
On the transmission side, 8-bit data to be transmitted are first converted into 10-bit data.
Then, the transmission data converted into 10-bit data are converted into serial data.
Thereafter, the transmission data converted into serial data are converted into an optical signal and transmitted over an optical fiber.
On the reception side, when the optical signal transmitted from the transmission side is received over the optical fiber, the received optical signal is first converted into an electric signal.
Then, a clock signal is extracted from the data converted into an electric signal and is converted into parallel data of 10 bits.
Thereafter, the 10-bit data converted into parallel data are converted into 8-bit data.
Serial optical transmission of data is realized by the sequence of processes described above.
However, when a large amount of data is transmitted, such serial transmission as described above increases the transmission amount per transmission line to such a level that transmission of the data cannot be realized. Particularly, transmission between clusters of computers is likely to suffer from the problem described above because a very large amount of data is transmitted.
Further, when serial transmission is carried out, parallel data must be converted into serial data, and this gives rise to another problem that a long processing time is required.
As a countermeasure for solving such problems as described above, realization of optical parallel transmission is demanded, and optical parallel transmission is being put into practical use to a certain extent.
FIG. 2
is a diagrammatic view illustrating a data transmission method in a conventional optical parallel transmission system.
On the transmission side, data of 8 bits to be transmitted and a clock signal are converted into an optical signal and transmitted over nine optical fibers provided in parallel.
On the reception side, when the optical signal transmitted from the transmission side is received over the optical fibers, the received optical signal is first converted into an electric signal.
Thereafter, skew adjustment is performed between the 8-bit data converted into the electric signal.
In such a conventional optical parallel transmission system as described above, when parallel data are transmitted as they are, it is often the case that data which include successive data of “0” cannot be transmitted in an AC fashion, and DC coupling by which a signal of successive “0”s or “1”s can be transmitted is demanded.
However, when it is tried to realize DC coupling, the module becomes expensive and is not practical. Besides, since various restrictions are applied, parallel transmission cannot be made taken advantage of.
Further, since parallel transmission of data produces a skew between data which is a difference in transmission time between transmission lines, there is a problem that a function of adjusting the skew must be newly added.
Furthermore, the optical parallel transmission system has many problems in regard to manufacture of parallel optical modules such as a yield and further has many problems also in regard to implementation of the same. However, in recent years, devices with which augmentation in yield can be achieved such as surface emitting lasers have exhibited remarkable augmentation in performance, and expectation for optical parallel transmission is increasing also due to perfection of modules.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical parallel transmission system which can achieve reduction of the processing time without adding many processing functions.
In the present invention, pattern data addition means adds, to transmission data, pattern data determined from the transmission data so that the transmission data per one bit becomes data having a form close to a repetition of “1”, “0”. Consequently, optical parallel transmission by AC coupling can be realized.
Further, since the pattern data addition means adds, to one or more positions of the transmission data, information for detecting synchronism among bits can be detected by synchronization processing means, so that there is no necessity of newly providing a function for adjusting a skew between bits of the transmission data.
Further, since it is discriminated by data discrimination means whether the transmission data is data which includes “1” and “0” or successive “0” data and a control signal for controlling processing on the reception side is produced based on the result of this discrimination and outputted, data transmission is performed smoothly.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.
REFERENCES:
patent: 6201829 (2001-03-01), Schneider
patent: 51-110206 (1976-09-01), None
patent: 5-227243 (1993-09-01), None
patent: 6-140992 (1994-05-01), None
patent: 8-37462 (1996-02-01), None
patent: 9-261174 (1997-10-01), None
NEC Corporation
Negash Kinfe-Michael
Sughrue & Mion, PLLC
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