Optical transmission device

An optical add/drop device for adding/dropping an optical signal, comprising:

• an optical add section for multiplexing an incoming WDM signal from a network with an optical add signal to generate a multiplexed signal;
• and
• an optical drop section including a wavelength selector and a reference wavelength monitor, the wavelength selector including a wavelength tunable filter for variably selecting a wavelength among those of the multiplexed signal in accordance with a control frequency, and a filter controller,
• the filter controller, performing:
• (a) applying the control frequency to the wavelength tunable filter,
• (b) detecting, based on a reference wavelength monitor signal supplied thereto, a reference control frequency which permits the wavelength tunable filter to select a reference wavelength and in accordance with which wavelength matching is performed,
• (c) obtaining, on reception of a wavelength selection request, a target control frequency based on the reference control frequency and a relative position of a target wavelength to be selected with respect to the reference wavelength, and
• (d) applying the target control frequency to the wavelength tunable filter, the reference wavelength monitor including a reference wavelength filter for transmitting the reference wavelength therethrough, and a light receiving element for monitoring the transmitted reference wavelength to generate the reference wavelength monitor signal;
• wherein the wavelength tunable filter includes a plurality of wavelength tunable filters, and the reference wavelength monitor is configured to multiplex outputs of the wavelength tunable filters and generate the reference wavelength monitor signal through a single reference wavelength filter,
• while one of the wavelength tunable filters is subjected to wavelength scan for the wavelength matching, output levels of the other wavelength tunable filters are lowered by the respective filter controllers, and the wavelength-matched wavelength tunable filter is applied with a frequency other than the reference control frequency until the wavelength matching of all of the wavelength tunable filters is completed.

An optical transmission device for transmitting an optical WDM signal, comprising:

• a wavelength selector including a wavelength tunable filter for variably selecting a wavelength in accordance with a control frequency, and a filter controller
• the filter controller, comprising the steps of:
• (a) applying the control frequency to the wavelength tunable filter,
• (b) detecting, based on a reference wavelength monitor signal supplied thereto, a reference control frequency which permits the wavelength tunable filter to select a reference wavelength and in accordance with which wavelength matching is performed,
• (c) obtaining, on reception of a wavelength selection request, a target control frequency based on the reference control frequency and a relative position of a target wavelength to be selected with respect to the reference wavelength, and
• (d) applying the target control frequency to the wavelength tunable filter;
• a reference wavelength monitor including a reference wavelength filter for transmitting the reference wavelength therethrough, and a light receiving element for monitoring the transmitted reference wavelength to generate the reference wavelength monitor signal;
• and
• a monitor for monitoring a wavelength transmitted through the wavelength tunable filter to generate a monitor signal, and wherein, when the target wavelength is to be selected by the wavelength tunable filter, the filter controller varies the control frequency in the vicinity of the target control frequency based on the monitor signal, to determine an optimum target control frequency;
• wherein, before the optimum target control frequency is determined, the filter controller applies the control frequency to the wavelength tunable filter with a level thereof set such that an output level of the wavelength tunable filter is lower than a minimum reception level of an optical receiver arranged at a stage succeeding the wavelength tunable filter, to prevent the optical receiver from receiving an optical signal.

An optical add/drop device for adding/dropping an optical signal, comprising:

• an optical add section for multiplexing an incoming WDM signal from a network with an optical add signal to generate a multiplexed signal;
• and
• an optical drop section including a wavelength selector and a reference wavelength monitor, the wavelength selector including a wavelength tunable filter for variably selecting a wavelength among those of the multiplexed signal in accordance with a control frequency, and a filter controller,
• the filter controller, comprising the steps of:
• (a) applying the control frequency to the wavelength tunable filter,
• (b) detecting, based on a reference wavelength monitor signal supplied thereto, a reference control frequency which permits the wavelength tunable filter to select a reference wavelength and in accordance with which wavelength matching is performed,
• (c) obtaining, on reception of a wavelength selection request, a target control frequency based on the reference control frequency and a relative position of a target wavelength to be selected with respect to the reference wavelength, and
• (d) applying the target control frequency to the wavelength tunable filter, the reference wavelength monitor including a reference wavelength filter for transmitting the reference wavelength therethrough, and a light receiving element for monitoring the transmitted reference wavelength to generate the reference wavelength monitor signal;
• wherein the optical drop section further includes a monitor for monitoring a wavelength transmitted through the wavelength tunable filter to generate a monitor signal, and when the target wavelength is to be selected by the wavelength tunable filter, the filter controller varies the control frequency in the vicinity of the target control frequency based on the monitor signal, to determine an optimum target control frequency;
• and wherein, before the optimum target control frequency is determined, the filter controller applies the control frequency to the wavelength tunable filter with a level thereof set such that an output level of the wavelength tunable filter is lower than a minimum reception level of an optical receiver arranged at a stage succeeding the wavelength tunable filter, to prevent the optical receiver from receiving an optical signal.