An apparatus includes an optical source of an optical wavelength carrier, an optical modulator to receive the optical wavelength carrier, and an optical data receiver. The optical data modulator is configured to produce, from the optical wavelength carrier, an optical signal to carry separate data on different first and second components thereof in individual modulation periods during data transmission and to carry a training sequence on one of the components during time slots for calibration. The first component is relatively phase offset from the second component in the optical signal. The optical data modulator alternates the one of the components between the first and second components over the time slots for calibration. The optical receiver is connected to receive a portion of the optical signal and to temporally interleave a measurement of a characteristic of the first component and a measurement of a characteristic of the second component over the time slots for calibration. The optical receiver is configured to feedback information to the optical data modulator based on the measured characteristics. The optical data modulator is configured to reduce an imbalance between the two components of the optical carrier during data transmission based on the information.

A decoding method includes: receiving a plurality of subcarrier signals each including encoded data; acquiring a predetermined amount of data from each of the plurality of subcarrier signals; correcting errors in the plurality of subcarrier signals by performing decoding arithmetic processing on the respective predetermined amounts of data acquired from the plurality of subcarrier signals in a time-division manner; and causing the decoding arithmetic processing to be consecutively performed on each of the predetermined amounts of data a predetermined number of times.

A system and method is disclosed in which circuitry of a first controller of a first node on a first path within a transport network receives a first signal indicating a failure within the first path from a second controller. The first node is an end node of the first path. A first client signal failure clear signal is received from a second node upstream of the first node on the first path. The first client signal failure clear signal indicates that a non-restorable fault has been resolved such that the first path can be considered for carrying data traffic. The non-restorable fault is a failure at the source. Subsequent to receiving the first signal indicating the failure within the first path, a backward defect indication clear signal is transmitted to the second node, the backward defect indication clear signal indicating an absence of a failure in the first path.

Consistent with the present disclosure independent phase and frequency clock recovery on each SC. Both leaf and hub perform digital clock recovery on each SC by increasing the Rx-ADC sampling rate by a few ppm (˜16 ppm), and using a delay compensating element, together with gapped clocks. The gaps and delay compensating elements are independent on each SC. The delay element is performed using the frequency domain DSP engine, where the frequency domain equalizer coefficients are modified with a delay compensating element Thus, each SC can have its own fine timing frequency and timing phase tuning, and fine tracking of its own jitter. When the delay compensating element, which, for example, may include a finite impulse response (FIR) filter, reaches the end of its range, a clock gap equal to an integer number of symbols is performed. The delay element can be reset by the same number of symbols providing continuous phase interpolation.

All-optical multi-rate systems and methods include and use a continuous wave (CW) light source for providing a CW carrier signal, a plurality of modulators used for modulating the CW carrier signal to form a plurality of modulated optical signals, an inverse filter bank for multiplexing the plurality of modulated optical signals to form a multiplexed optical signal, and a post distortion filter (PDF) for obtaining a narrowed multiplexed optical signal and, optionally, for eliminating inter-symbol interference (ISI) in the narrowed multiplexed optical signal.

Consistent with the present disclosure a network is provided that includes a primary node and a plurality of secondary nodes. The primary node, as well as each of the secondary nodes, includes a laser that is “shared” between the transmit and receive sections. That is, light output from the laser is used for transmission as well as for coherent detection. In the coherent receiver, the frequency of the primary node laser is detected and, based on such detected frequency, the frequency of the secondary node laser is adjusted to detect the received information or data. Such frequency detection also serves to adjust the transmitted signal frequency, because the laser is shared between the transmit and receive portions in each secondary receiver. Light output from the primary node laser, which is also shared between transmit and receive portions in the primary node, is thus also set to a frequency that permits detection of each of the incoming optical signals by way of coherent detection. Since, in this example, only one laser is employed in the primary node, the primary node may have a simpler design and may be less expensive to manufacture compared to a primary node having multiple local oscillator lasers, each associated with a corresponding uplink optical signal.

The invention is a datacenter network comprising a plurality of switches. The switches comprise edge switches and aggregation switches associated with sliceable bandwidth variable transceivers (S-BVT). An intermediate passive optical layer is communicatively coupled to the edge switches and the aggregation switches via fiber optic links associated with the S-BVTs. Furthermore, the intermediate passive optical layer is inserted between the edge and aggregation layers in order to combine the signals from each tier. The intermediate passive optical layer comprises a passive fiber coupler that combines the links between switches and each S-BVT receiver receives the signals sent from all S-BVT transmitters connected to the intermediate passive optical layer. The datacenter network is adapted to adjust the local oscillator wavelength of each S-BVT receiver and the wavelength and slice allocation of each S-BVT transmitter, thereby permitting dynamically allocating different resources to each link.

An optical transmission apparatus (1_1) according to the present invention includes a first transmission unit (11_1) that transmits a first optical transmission signal (21_1), a second transmission unit (11_2) that transmits a second optical transmission signal (21_2), and an output unit that outputs, when the first optical transmission signal (21_1) and the second optical transmission signal (21_2) share a set of information, both the first optical transmission signal (21_1) and the second optical transmission signal (21_2) to a first path (26_1) and outputs, when the first optical transmission signal (21_1) and the second optical transmission signal (21_2) do not share the set of information, one of the first optical transmission signal (21_1) and the second optical transmission signal (21_2) to a second path (26_2).

To suppress the deterioration of the characteristics of a MIMO equalizer as well as minimizing an increase in circuit size in spite of the occurrence of signal spectrum narrowing and asymmetric spectrum degradation, a wavelength-division multiplexing optical transmission system (10) according to an embodiment includes a transmitter (1) that generates one channel signal by wavelength-division multiplexing a plurality of subcarrier signals so as to overlap each other and transmits the channel signal, and a receiver (2) that separates a received channel signal into subcarrier signals, and performs equalization using an MIMO equalizer (3) including a FDE-MIMO equalizer (4) and a TDE-MIMO equalizer (5) on each of the separated subcarrier signals.

Optical network systems are disclosed, including a transmitter comprising a digital signal processor that receives data; circuitry that generate a plurality of electrical signals based on the data; a plurality of filters, each of which receiving a corresponding one of the plurality of electrical signals, a plurality of roll-off factors being associated with a respective one of the plurality of filters; a plurality of digital-to-analog converter circuits that receive outputs from the digital signal processor, the outputs being indicative of outputs from the plurality of filters; a laser that supplies light; and a modulator that receives the light and outputs from the digital-to-analog converter circuits, the modulator supplying a plurality of optical subcarriers based on the outputs of the digital-to-analog converter circuits, such that one of the plurality of optical subcarriers carrying information for clock recovery.