82 results about "Wdm transmission" patented technology

A coolerless photonic integrated circuit (PIC), such as a semiconductor electro-absorption modulator / laser (EML) or a coolerless optical transmitter photonic integrated circuit (TxPIC), may be operated over a wide temperature range at temperatures higher then room temperature without the need for ambient cooling or hermetic packaging. Since there is large scale integration of N optical transmission signal WDM channels on a TxPIC chip, a new DWDM system approach with novel sensing schemes and adaptive algorithms provides intelligent control of the PIC to optimize its performance and to allow optical transmitter and receiver modules in DWDM systems to operate uncooled. Moreover, the wavelength grid of the on-chip channel laser sources may thermally float within a WDM wavelength band where the individual emission wavelengths of the laser sources are not fixed to wavelength peaks along a standardized wavelength grid but rather may move about with changes in ambient temperature. However, control is maintained such that the channel spectral spacing between channels across multiple signal channels, whether such spacing is periodic or aperiodic, between adjacent laser sources in the thermally floating wavelength grid are maintained in a fixed relationship. Means are then provided at an optical receiver to discover and lock onto floating wavelength grid of transmitted WDM signals and thereafter demultiplex the transmitted WDM signals for OE conversion.

A hybrid external cavity multi-wavelength laser using a QD RSOA and a silicon photonics chip is demonstrated. Four lasing modes at 2 nm spacing and less than 3 dB power non-uniformity were observed, with over 20 mW of total output power. Each lasing peak can be successfully modulated at 10 Gb / s. At 10−9 BER, the receiver power penalty is less than 2.6 dB compared to a conventional commercial laser. An expected application is the provision of a comb laser source for WDM transmission in optical interconnection systems.

A method for protecting WDM transmission. On the first transmission direction, the first node implements service transmission to the second node by selecting one from the two transmission paths protected by each other, the second node implements two-path reception based on the two transmission paths; on the second transmission direction contrary to the first transmission direction, the second node implements two-path service sending via the two transmission paths protected by each other, the first node implements reception by selecting one from the two transmission paths. A system for implementing the WDM transmission protection and an apparatus thereof.

An optical receiver is provided for reducing in scale the overall system for wavelength division multiplex transmission lines configured redundantly and improving the quality of transmission when the line is switched. The optical receiver includes a variable optical attenuator for controlling an optical loss value for each optical transmission line based on a predetermined optical loss value. A variable dispersion compensation module is also provided for controlling a wavelength dispersion value for each optical transmission line based on a predetermined dispersion value. An optical loss / dispersion controller is also provided for measuring the optical loss value and the wavelength dispersion value of every optical transmission line, outputting the predetermined optical loss value and dispersion value so that the optical loss values and the wavelength dispersion values are equal in all the optical transmission lines, and controlling the variable optical attenuator and the variable dispersion compensation module based on the outputted predetermined values. A receive amplifier is also provided for receiving the optical signal whose light level is kept constant and amplifying the signal. Also, a transmission line switch control module is provided for switching a working transmission line into a protection line if the optical signal level of the working line is lower than a threshold value.

Efficient wavelength calibration in a WDM optical amplifier that includes an optical channel monitor (OCM) is obtained by introducing a notch into the amplified spontaneous emission (ASE) noise spectrum of the amplifier outside a WDM transmission band, and having the OCM detect the notch and use the notch as a reference to calibrate the wavelength measurement. The notch is introduced into the ASE noise spectrum using a notch filter, which is preferably incorporated in a gain flattening filter (GFF).

An optical fiber includes a first core having a relative refractive index difference of larger than 0.36%, and a cladding. The optical fiber has fiber cut-off wavelength lambdac of more than 1350 nm, cable cut-off wavelength lambdacc of less than 1285 nm, bending loss at a wavelength of 1625 nm of not more than 10 dB / km when wound at a diameter of 20 mm, transmission loss at a wavelength range of 1285 to 1625 nm of not more than 0.40 dB / km, transmission loss at a wavelength of 1383 nm less than transmission loss at a wavelength of 1310 nm, and difference in transmission loss at a wavelength of 1383 nm of not more than 0.04 dB / km before and after exposure to hydrogen. The lower bending loss of the optical fiber provides an optical fiber cable for use in a WDM transmission in wavelength range of 1285 to 1625 nm.

Full-mesh WDM transmission units, each of which includes n number of interfaces and is capable of establishing a bidirectional full-mesh communication between all of the interfaces using wavelength paths based on a wavelength division multiplexing technique, are connected in a multistage tree-shaped structure by internetwork connection units through edge-packet transfer units connected to the respective interfaces. Therefore, it is possible to hold a direct communication between user terminals connected to the edge-packet transfer units of the same full-mesh WDM transmission unit, and to realize scalability by a multistage connection configuration.

An integrated optical dynamic channel equalizer that can be employed to equalize the channel gain level in a WDM transmission line and monitor the optical channel performance. The device consists of a circulator, a dynamic gain equalizer chip and a controller. Due to the simplicity of the dynamic gain equalizer chip, which includes one 1×n multiplexer / demultiplexer, an n-channel variable optical attenuator array (VOA-n), a partially transparent dielectric reflective means and an n-channel detector array, the device is very compact and can be fabricated at low cost. By placing a quarter wave plate between the n-channel variable optical attenuator array and the partially transparent reflective means in the dynamic channel equalizer chip, the device can be rendered polarization insensitive.

The present invention includes various novel techniques, apparatus, and systems for optical WDM communications that involve dynamically modifying certain aspects of the WDM transmission (and corresponding receive) process at the optical (physical) layer to significantly enhance data / network security. These various dynamic modifications can be employed individually or in combination to provide even greater security depending upon the desired application and design tradeoffs. WDM transmission steps typically include encoding the client signals, mapping them to one or more subchannels within or across ITU channels, modulating them onto subcarrier frequencies, and multiplexing them together for optical transmission. By dynamically modifying one or more of these processing steps over time (in addition to any encryption of the underlying client signals), the current invention provides additional security at the physical (optical) layer of an optical network and thus greatly enhances overall network security.

The present invention relates to an optical fiber comprising a structure enabling WDM transmissions by utilizing the whole wavelength range of 1300 nm to 1625 nm as a signal wavelength band. In the optical fiber according to the present invention, the transmission loss is 0.4 dB / km or less at a wavelength of 1310 nm, 0.4 dB / km or less at a wavelength of 1383 nm, and 0.3 dB / km or less at a wavelength of 1550 nm. The chromatic dispersion is 0.1 ps / nm / km or more but 5.5 ps / nm / km or less at a wavelength of 1383 nm, and 0.1 ps / nm / km or more but 16.5 ps / nm / km or less in the wavelength range of 1530 nm to 1565 nm. The cut off wavelength at a length of 22 m is 1300 nm or less, and the absolute value of dispersion slope in the wavelength range of 1300 nm to 1625 nm is 0.1 ps / nm2 / km or less.

A WDM signal light monitoring device includes a first monitor for monitoring input-side WDM main signal light and output-side WDM main signal light for each wavelength; and a second monitor for monitoring the first monitor by comparing a monitoring result received from an upstream WDM transmission device with a monitoring result of the first monitor, wherein the monitoring result of the first monitor is transmitted to a downstream WDM transmission device in the system.

The present invention discloses a submarine observation system in which a plurality of carrier lights assigned to each submarine observation equipment is transmitted from a land terminal apparatus to an optical submarine cable (down-going) by using a WDM transmission. In the submarine observation equipment, only a prescribed carrier light is demultiplexed by an optical demultiplexer, an observation signal indicating an observation result is generated by an observation device, intensity of the carrier light demultiplexed by the optical demultiplexer is modulated by an optical amplifier based on an observation signal, and the modulated carrier light is multiplexed by an optical multiplexer. The multiplexed carrier light is output to the optical submarine cable (up-going) to be returned to the land terminal apparatus being the transmission station. The land terminal apparatus is able to obtain an observation signal of each observation point by separating carrier lights based on each wavelength and receiving a separated carrier light of each wavelength. Accordingly, the system can be structured with one optical fiber and can be extendable by increasing or decreasing carrier lights, and either one of the land terminal apparatuses can receive an observation signal even when the optical submarine cable is cut off.

The present document relates to optical communication systems. In particular, the present document relates to high efficiency wavelength division multiplexing (WDM) optical communication systems. An optical transmitter (210) adapted to transmit an optical signal on an optical wavelength division multiplexed, referred to as WDM, transmission channel (111) to a corresponding optical receiver (230) is described. The optical transmitter (210) comprises a profiling unit (217) adapted to receive information regarding an equalization filter (270) adapted at the corresponding optical receiver (230), based on a first optical signal received from the optical transmitter (210); a pulse shaping filter unit (212) adapted to filter a sequence of data symbols (211) using a pulse shaping filter, thereby yielding a filtered sequence of data symbols (211); wherein a frequency response (404, 405) of the pulse shaping filter depends on the information regarding the equalization filter (270); and a digital-to-optical converter (214, 215 216) adapted to convert the filtered sequence of data symbols (211) into a second optical signal to be transmitted to the optical receiver (230).

An optical amplifier that improves the quality of WDM transmission by reducing four-wave mixing. An optical fiber has positive chromatic dispersion in a signal band and is used as an optical amplification medium for amplifying a wavelength division multiplex signal. An excitation section inputs excitation light to the optical fiber. In order to actualize mismatching of phases of optical signals with different wavelengths to be propagated, the optical fiber has positive chromatic dispersion in a signal band by which there is a great difference between a signal frequency, being a frequency of a signal to be amplified, and a zero-dispersion frequency, being a frequency at which chromatic dispersion is zero. As a result, the optical fiber functions as an optical amplification medium in which four-wave mixing is suppressed.

The present invention discloses a submarine observation system in which a plurality of carrier lights assigned to each submarine observation equipment is transmitted from a land terminal apparatus to an optical submarine cable (down-going) by using a WDM transmission. In the submarine observation equipment, only a prescribed carrier light is demultiplexed by an optical demultiplexer, an observation signal indicating an observation result is generated by an observation device, intensity of the carrier light demultiplexed by the optical demultiplexer is modulated by an optical amplifier based on an observation signal, and the modulated carrier light is multiplexed by an optical multiplexer. The multiplexed carrier light is output to the optical submarine cable (up-going) to be returned to the land terminal apparatus being the transmission station. The land terminal apparatus is able to obtain an observation signal of each observation point by separating carrier lights based on each wavelength and receiving a separated carrier light of each wavelength. Accordingly, the system can be structured with one optical fiber and can be extendable by increasing or decreasing carrier lights, and either one of the land terminal apparatuses can receive an observation signal even when the optical submarine cable is cut off.