Planar assemblies for optical transceivers

Planar assemblies for coupling a plurality of optical transceivers to the same optical fiber. For example, the optical transceivers may be PON transceivers functioning according to different data rates and/or different modulation formats. Each optical transceiver communicates using one or more different wavelength channels. At least some of the disclosed planar assemblies are scalable to couple various numbers of optical transceivers to the same end face of an optical fiber, e.g., by fixing a corresponding number of passive, slab-like optical filters to a substantially planar surface of the support substrate to which the optical transceivers are also fixed adjacent and along. Some embodiments may employ various bulk lenses fixed to said planar surface to suitably relay light-beam segments between the end face of the fiber and the optical transceivers and/or between the different slab-like optical filters.

BACKGROUND

Field

Various example embodiments relate to optical communication equipment and, more specifically but not exclusively, to optical transmitters and receivers.

Description of the Related Art

A fiber-optic system typically employs an optical transmitter at one end of an optical fiber line and an optical receiver at the other end of the optical fiber line. Some fiber-optic systems operate by transmitting in one direction on one carrier wavelength and in the opposite direction on another carrier wavelength to achieve full duplex (FDX) operation. An FDX system can be implemented using optical transceivers, wherein each optical transceiver includes a respective optical transmitter and a respective optical receiver, which may be physically integrated. The telecom industry and its suppliers develop, manufacture, sell, and use a large variety of optical transceivers for many different applications.

SUMMARY OF SOME SPECIFIC EMBODIMENTS

Some embodiments herein include planar assemblies enabling the coupling of a plurality of optical transceivers to the same optical fiber. For example, the optical transceivers may be passive-optical-network (PON) transceivers functioning according to different data rates and/or different modulation formats. Each optical transceiver communicates using one or more different wavelength channels. At least some of the disclosed planar assemblies belong to scalable architectures. Thus, the planar assemblies may be in embodiments coupling various numbers of optical transceivers to the same end face of an optical fiber, e.g., by fixing a corresponding number of passive, slab-like optical filters to a substantially planar surface of the support substrate to which the optical transceivers are also fixed adjacent and along. Some embodiments may employ various bulk lenses fixed to said planar surface to suitably relay light-beam segments between the end face of the fiber and the optical transceivers and/or between the different slab-like optical filters. In some embodiments, a planar assembly may be configured to couple some of the optical transceivers to end faces of at least two different optical fibers.

According to an example embodiment, provided is an apparatus comprising: a substrate having a substantially planar surface; first and second optical transceivers fixed to said substrate adjacent and along said planar surface, the first and second optical transceivers having non-overlapping footprints on said planar surface; and a passive optical filter fixed to said substrate and configured to direct along said planar surface, between an end face of an optical fiber and the first optical transceiver, light of first wavelengths, and to direct along said planar surface, between the end face and the second optical transceiver, light of second wavelengths, the first wavelengths being different from the second wavelengths.

In some embodiments of the above apparatus, the apparatus further comprises a connector fixed to the substrate to stabilize an end segment of the optical fiber along said planar surface, the end segment including the end face.

DETAILED DESCRIPTION

FIG.1shows a block diagram of an optical communication system100according to an embodiment. System100comprises wavelength-division-multiplexing (WDM) transceivers102Wand102Econnected using a fiber-optic link150. For illustration purposes and to simplify the description, WDM transceivers102Wand102Eare referred-to herein as being located at the West and East ends, respectively, of link150. This notation should not be interpreted to imply any preference or limitation with respect to the geo-positioning of system100. For example, one of the WDM transceivers, e.g., transceiver102Wmay have some of its individual transceivers110located at relatively remote locations.

In some embodiments, system100complies with the ITU-T G.709/Y.1331 Recommendation, which is incorporated herein by reference in its entirety.

In an example embodiment, link150can be implemented using one or more spans of optical fiber140. In addition, link150may optionally have one or more optical amplifiers (not explicitly shown inFIG.1), e.g., each connected between ends of two respective spans of fiber140. In some embodiments, link150may incorporate additional optical elements (not explicitly shown inFIG.1), such as optical splitters, combiners, couplers, switches, etc., as known in the pertinent art. In some embodiments, link150may not have any optical amplifiers therein.

In an example embodiment, WDM transceivers102Wand102Eare configured to use carrier wavelengths λ1-λ2N, with the carrier wavelengths λ1-λNbeing used to transmit optical signals in the Eastward direction, and the carrier wavelengths λN+1-λ2Nbeing used to transmit optical signals in the Westward direction. In some embodiments, the carrier wavelengths may be arranged on one or more frequency (wavelength) grids, such as the frequency grids that comply with one or more of ITU-T G.694.1, ITU-T G.989.2, and ITU-T G.9807 Recommendations, which are incorporated herein by reference in their entirety. For example, different respective frequency grids may be used for the Eastward and Westward directions.

In an example embodiment, a frequency grid used in system100can be defined, e.g., in a frequency range between about 180 THz and about 220 THz, with a 500, 200, 100, 50, 25, or 12.5-GHz spacing of the channels therein. While typically defined in frequency units, the parameters of the grid can equivalently be expressed in wavelength units. For example, in the wavelength range from about 1528.8 nm to about 1563.9 nm, the 100-GHz spacing between the centers of neighboring WDM channels is equivalent to approximately 0.8 nm spacing. In alternative embodiments, other suitable frequency grids (e.g., flexible or having other spacing grids) can also be used.

In some embodiments, system100can be configured to transport polarization-division-multiplexed (PDM) signals, wherein each of the two orthogonal polarizations of each optical WDM channel can be used to carry a different respective data stream.

In an example embodiment, WDM transceiver102Wcomprises N individual transceivers1101W-110NW, where the number N is an integer greater than one. Each of transceivers1101W-110NWcomprises a respective optical transmitter (not explicitly shown inFIG.1; e.g., seeFIGS.3-4) configured to generate a respective WDM component of the Eastward-propagating optical WDM signal using a different respective carrier wavelength (e.g., one of wavelengths λ1-λN, as indicated inFIG.1). A multiplexer/demultiplexer (MUX/DMUX)120Woperates to combine (multiplex) these WDM components, thereby generating the corresponding Eastward-propagating optical WDM signal that is applied to link150for transmission to WDM transceiver102E.

Each of transceivers1101W-110NWfurther comprises a respective optical receiver (not explicitly shown inFIG.1; e.g., seeFIGS.3-4) configured to detect a respective WDM component of the Westward-propagating optical WDM signal received through link150from WDM transceiver102E. MUX/DMUX120Woperates to separate (demultiplex) the WDM components of the received Westward-propagating optical WDM signal, thereby generating optical input signals for the optical receivers of the individual-channel transceivers1101W-110NW. In an example embodiment, each of such optical input signals has a different respective carrier wavelength (e.g., one of wavelengths λN+1-λ2N, as indicated inFIG.1).

In an example embodiment, WDM transceiver102Ecan be constructed using components similar to those of WDM transceiver102Wand configured to operate in a similar manner. A description of WDM transceiver102Efor such embodiments can therefore be substantially obtained from the above description of WDM transceiver102W, e.g., by interchanging the subscripts E and W.

In some embodiments, system100may be constructed to implement a passive optical network (PON) or a part thereof. A typical PON has a point-to-multipoint architecture in which a passive optical router (e.g., a passive optical splitter) is used to enable an optical line terminal (OLT) located at a central office to send data transmissions to and receive data transmissions from optical network units (ONUs) located at different respective customer sites. In such embodiments, WDM transceiver102Wmay be a part of the OLT and be constructed such that different components thereof are not farther away from each other than about 10 m. On the other hand, in a typical PON embodiment of system100, some of individual transceivers1101E-110NEmay be separated from one another by relatively large distances, e.g., more than 20 m, and more typically by about 100 m or more. Also, MUX/DMUX120Emay be implemented using a passive optical router whose one or more components are located at a relatively large distance, e.g., 1 km or more, from any one of the individual transceivers1101E-110NE.

FIG.2shows a schematic top view of an electro-optical device200that can be used to implement an individual optical transceiver110(FIG.1) according to an embodiment. For illustration purposes and without any implied limitations, device200is described below with wavelength notations corresponding to a transceiver110nE, where 1≤n≤N (also seeFIG.1). As described, device200can be used, e.g., in some of the above-described PON embodiments of system100. A person of ordinary skill in the art will understand, without any undue experimentation, how to adapt device200for any pertinent uses in system100and/or other optical communication systems.

Device200is constructed using a plurality of components and discrete elements appropriately arranged and mounted on a main surface of a substrate202, e.g., a substantially planar surface. In other words, substrate202is a common substrate to some or all of those components and discrete elements. Some components and/or discrete elements may be mounted on substrate202using appropriate support structures, e.g., holders, mounts, connectors, etc., attached to the main surface of the substrate. The heights of such support structures may vary and be selected, e.g., to provide proper optical alignment within device200.

As used herein, the term “substrate” refers to a circuit or device carrier, a plate, a board, or a base designed and configured to provide and/or support electrical and/or optical connections between different parts thereof to enable proper operation of electrical, optical, and/or optoelectronic components located at, mounted on, or connected to those parts. Such components may include any combination of packaged or non-packaged electronic integrated circuits, photonic integrated circuits, and discrete (e.g., lumped) elements. Electrical connections between different parts of the substrate can be formed, e.g., using patterned conducting (such as metal) layers located within the body or on the surface of the substrate and/or conventional electrical wiring. Optical connections between different optical and/or optoelectronic components on the substrate can be formed through free space, e.g., using discrete optical elements mounted on the substrate. In some embodiments, the substrate may have several distinct levels, e.g., comprising a redistribution layer (RDL), an interposer, a laminated plate, and/or a printed circuit board.

In some example embodiments, a substrate can be implemented using a semiconductor wafer, e.g. a silicon or silicon on insulator (SOI) wafer substrate, or a silicon optical bench (SiOB). A main surface of such a substrate can be micromachined to enable precise optical alignment of various optical components placed thereon.

In some embodiments, a substrate can be a substrate whose lateral dimensions (e.g., length and width) are significantly larger than its thickness. In the view shown inFIG.2, the thickness of substrate202is the dimension thereof measured along the Z-coordinate axis, and the lateral dimensions are the dimensions measured along the X- and Y-coordinate axes. An exterior surface of substrate202that is substantially parallel to the XY-coordinate plane may be referred to as a “main” surface of the substrate. In contrast, exterior surfaces of the substrate that have one relatively large size, e.g., length, and one relatively small size, e.g., height, may typically be referred to as the edges of the substrate.

A main surface of a substrate may be referred to as being substantially planar if feature-height variation thereon is significantly smaller than the smaller one of the two lateral sizes of the substrate. In some cases, a main surface of a substrate may be referred to as being substantially planar if the feature-height variation thereon is significantly smaller than the thickness of the substrate.

Device200comprises a laser210, a photodiode (e.g., an avalanche photodiode, APD)270, and an optical fiber290, all mounted on a main (e.g., top) surface of substrate202to appropriately optically couple the laser and photodiode to a proximate end288of the fiber. Laser210can be used in the optical transmitter of the corresponding transceiver110. Photodiode270can be used in the optical receiver of the corresponding transceiver110.

In an example embodiment, laser210is a directly modulated laser configured to emit light of carrier wavelength λN+n. In operation, laser210emits modulated light in response to a drive signal received through an electrical port208, e.g., from an external drive circuit or data source. Relay optics, e.g., comprising ball lenses214and284, is used to couple the emitted light, through end288, into optical fiber290. Ball lenses214and284are both mounted on the top surface of substrate202.

In some embodiments, laser210may be replaced, e.g., as known in the pertinent art, by a pulsed or continuous-wave (CW) laser outfitted with an external (e.g., located outside the laser cavity) optical modulator.

Photodiode270is optically coupled to end288of fiber290using ball lenses266and284. Similar to ball lenses214and284, ball lens266is mounted on the top surface of substrate202. In response to light received from fiber290, photodiode270generates a corresponding electrical output272, which is then amplified using an electrical amplifier (e.g., transimpedance amplifier, TIA)280. A resulting amplified signal is applied to an electrical port282for transmission to external circuits. In some embodiments, electrical amplifier280can be implemented using an integrated circuit mounted on the top surface of substrate202.

In some embodiments, optical fiber290may be supported on a separate support structure, e.g., a fiber connector that is not mounted on substrate202. The end segment of optical fiber290having the end face288may be oriented, e.g., substantially orthogonally to the main surface of substrate202, and a mirror (not shown inFIG.2) may be used in a conventional manner to change the propagation direction of the corresponding light beam(s) for efficient light coupling into and out of the optical fiber290so oriented. In some embodiments, the orientation angle of the optical fiber290with respect to the main-surface normal can be any suitable angle between 0 and 90 degrees.

Device200further comprises an optical wavelength diplexer230mounted on the top surface of substrate202and optically coupled to ball lenses214,266, and284, e.g., as indicated inFIG.2. Wavelength diplexer230is an optical filter that: (i) passes through (e.g., transmits) optical signals in an optical band corresponding to the wavelength λN+n; and (ii) redirects (e.g., reflects) optical signals in a different optical band corresponding to the wavelength λn.

In an example embodiment shown inFIG.2, diplexer230is implemented using a rectangular slab made of an optically transparent material (e.g., glass) that has one or more thin dielectric films deposited on one or both sides thereof. The optical properties and the thickness of the slab230and/or the thin film(s) thereon are selected such as to support the above-indicated spectral function of the diplexer. The orientation of the slab230is such that: (i) an optical signal of carrier wavelength λN+nemitted by laser210passes through the slab and is coupled into fiber290; and (ii) an optical signal of carrier wavelength λnemitted by fiber290is reflected by the slab and impinges on photodiode270.

Although, as shown inFIG.2, the slab230is oriented at 45 degrees with respect to the optical axis corresponding to ball lenses214and284, other orientation angles can also be used in some alternative embodiments. A person of ordinary skill in the art will understand how to reposition ball lens266and photodiode270to achieve proper optical alignment/coupling of the latter in such alternative embodiments. In some alternative embodiments, an additional optical element, such as an angled mirror (not shown inFIG.2), may be used to properly orient the various relevant light beam segments with respect to the slab230.

Device200further comprises an optical isolator220located between diplexer230and lens214. Optical isolator220is mounted on the top surface of substrate202. In operation, optical isolator220transmits light substantially in one direction, e.g., as indicated inFIG.2. This property of optical isolator220is used to prevent unwanted feedback into an optical oscillator (e.g., cavity) of laser210.

Device200further comprises an optical filter240located between diplexer230and lens266. Filter240is mounted on the top surface of substrate202. The optical properties of filter240are selected such as to prevent most of spurious unwanted light from reaching photodiode270. In an example embodiment, filter240can be a conventional band-pass optical filter or a low-pass optical filter, e.g., implemented using a colored glass plate.

In some embodiments, photodiode270can be replaced by a photodetector that enables coherent detection. Such a photodetector may include two or more photodiodes and, in some embodiments, an optical mixer, such as an optical hybrid or a polarization mixer. For such embodiments, a person of ordinary skill in the art will understand how to modify or replace amplifier280to make the resulting electrical circuit compatible with the used photodetector.

In some embodiments, some or all of ball lenses214,266, and284may be made of different respective materials (e.g., having different refractive indices) to adjust beam sizes and/or have different sizes (e.g., diameters) to adjust the beam-segment heights and angles.

In some embodiments, some or all of ball lenses214,266, and284may be replaced by suitable lenses of other shapes, e.g., various bulk optical lenses.

FIG.3illustrates a three-dimensional perspective view of electro-optical device200(FIG.2) according to an embodiment. More specifically,FIG.3shows an angled top view of device200in which a substantially planar top surface302of substrate202is clearly visible. In the shown embodiment, top surface302is textured for better and/or more-convenient attachment thereto of the various device components. Top surface302also has a shallow groove330that has a width and orientation that enable easier and/or more accurate placement and attachment of the diplexer slab230on surface302. Top surface302further has a shallow groove340that has a width and orientation that enable and/or more accurate easier placement and attachment of the filter plate240. The angle α between the grooves330and340is, e.g., 45 degrees.

As shown inFIG.3, device200comprises a holder390configured to fixedly hold the end segment of fiber290at a proper height and orientation, slightly above top surface302. In some embodiments, holder390may have a V-shaped groove into which the end segment of fiber290can be conveniently inserted. Holder390is mounted on and directly attached to top surface302.

Other components and elements of device200that have been previously described in reference toFIG.2are labeled inFIG.3using the same reference numerals.

FIG.4shows a schematic top view of an electro-optical device400that can be used to implement a WDM transceiver102(FIG.1) according to an embodiment. The shown embodiment corresponds to N=2 (also seeFIG.1). For illustration purposes and without any implied limitations, device400is described below with wavelength notations corresponding to WDM transceiver102W. As described, device400can be used, e.g., in some of the above-described PON embodiments of system100. A person of ordinary skill in the art will understand, without any undue experimentation, how to adapt device400for any pertinent uses in system100and/or other optical communication systems.

Device400is constructed using many of the same device elements/components as those used in device200(FIGS.2-3). Such device elements/components are labeled inFIG.4using the same numerical labels as inFIG.2. Label subscripts are used inFIG.4to indicate possible differences in the spectral characteristics of otherwise analogous device elements/components.

Device400comprises optical assemblies4021and4022, both mounted on a main surface of substrate202. According to the terminology used in some relevant literature, each of optical assemblies4021and4022may be referred to as a bidirectional optical sub-assembly or BOSA. That is, each of the optical assemblies4021and4022is configured to transmit and receive light via the corresponding same optical path.

In an example embodiment, optical assemblies4021and4022can be used to implement, e.g., individual optical transceivers1101Wand1102W, respectively. In such an embodiment, optical assembly4021is configured to operate using carrier wavelengths λ1and λ3; and optical assembly4022is configured to operate using carrier wavelengths λ2and λ4.

An optical wavelength diplexer430is used in device400to appropriately route the corresponding optical signals between fiber290and optical assemblies4021and4022, e.g., as indicated inFIG.4. Optical wavelength diplexer430is mounted on the top surface of substrate202and can be implemented using a filter slab similar to that used to implement optical wavelength diplexer230, e.g., as described above (also seeFIGS.2-3). In operation, optical wavelength diplexer430: (i) passes through the optical signals corresponding to the wavelengths λ1and λ3; and (ii) reflects at an angle the optical signals corresponding to the wavelengths λ2and λ4. The optical signals corresponding to the wavelengths λ1and λ3are coupled to optical assembly4021as indicated inFIG.4. The optical signals corresponding to the wavelengths λ2and λ4are coupled to optical assembly4022as further indicated inFIG.4. The latter optical coupling can be aided by the optional relay optics, e.g., comprising ball lenses414and484mounted on the top surface of substrate202.

In optical assembly4021, laser2101is configured to emit light of carrier wavelength λ1. Optical wavelength diplexer2301, which is optically coupled to optical wavelength diplexer430as indicated inFIG.4, is an optical filter that: (i) passes through the optical signals in an optical band corresponding to the wavelength λ1; and (ii) reflects at an angle the optical signals in an optical band corresponding to the wavelength λ3. The optical properties of optical filter2401are such as to prevent most of spurious unwanted light from reaching the adjacent photodiode270, while allowing the optical signals corresponding to the wavelength λ3to impinge on that photodiode.

In optical assembly4022, laser2102is configured to emit light of carrier wavelength λ2. Optical wavelength diplexer2302, which is optically coupled to optical wavelength diplexer430as indicated inFIG.4, is an optical filter that: (i) passes through the optical signals in an optical band corresponding to the wavelength λ2; and (ii) reflects at an angle the optical signals in an optical band corresponding to the wavelength λ4. The optical properties of optical filter2402are such as to prevent most of spurious unwanted light from reaching the adjacent photodiode270, while allowing the optical signals corresponding to the wavelength λ4to impinge on that photodiode.

In some embodiments, one or both of ball lenses414and484may be replaced by suitable lenses of other shapes, e.g., various bulk optical lenses.

FIG.5shows a schematic top view of an electro-optical device500that can be used to implement a WDM transceiver102(FIG.1) according to another embodiment. Although the shown embodiment corresponds to the number N>3 (also seeFIG.1), a person of ordinary skill in the art will understand how to scale and/or modify device500to adapt it to N=3 and/or to any technically feasible integer value of the number N, with N≥2. In this respect, device500provides an example of a scalable architecture, e.g., because it lends itself to relatively easy redesign for a different value of the number N by adding or removing a corresponding number of optical assemblies402and the corresponding filters430. Some embodiments of device500also lend themselves to a relatively straightforward fabrication process, wherein different components are picked and placed on substrate202to produce free-space optical connections for the N transceivers of the device on the same substrate.

Device500is constructed using many of the same device elements/components as those used in device400(FIG.4). Such device elements/components are labeled inFIG.5using the same numerical labels as inFIG.4. Label subscripts are used inFIG.5to indicate possible differences in the spectral characteristics of otherwise analogous device elements/components.

Device500comprises an array of optical assemblies4021-402Nmounted on a main (e.g., top) surface of substrate202. Optical assemblies4021and4022are labeled inFIG.5as4021′ and4022′ to indicate that different ones of these optical assemblies may be configured to use different sets of wavelengths than those indicated in reference toFIG.4. In an example embodiment, each of optical assemblies4021-402NofFIG.5may have a planar structure similar to that described in reference toFIG.4for optical assemblies4021and4022shown therein.

Optical assembly4021′ is configured to use carrier wavelengths λ1and λN+1. Optical assembly4022′ is configured to use carrier wavelengths λ2and λN+2. Optical assembly4023is configured to use carrier wavelengths λ3and λN+3, and so on. Optical assembly402Nis configured to use carrier wavelengths λNand λ2N.

Device500further comprises a passive optical router530that operates to provide proper wavelength routing between optical fiber290and the various ones of optical assemblies4021-402N. In an example embodiment, optical router530is a substantially planar optical device mounted on the top surface of substrate202. As shown, optical router530comprises a sequence of optical wavelength diplexers4301-430Nand relay-optics sub-systems, wherein each of such sub-systems employs a respective pair of ball lenses414and484. A person of ordinary skill in the art will understand that the shown placement of ball lenses414and484represents a non-limiting example of how the relay optics of device500can be configured and that other lens configurations are also possible. For example, some or all of the ball lenses414and484can be moved from the “through” optical path of passive optical router530to the corresponding “drop” optical paths, i.e. the optical paths between optical wavelength diplexers430and optical assemblies402.

In an example embodiment, optical router530may have a plurality of bidirectional optical ports that include: (i) a first optical port528; and (ii) N second optical ports532i-532N. Optical port528transmits light propagating between optical wavelength diplexer4301and end288of fiber290. Optical port5321transmits light propagating between optical wavelength diplexer4301and optical assembly4021′. Optical port5322transmits light propagating between optical wavelength diplexer4302and optical assembly4022′. Optical port5323transmits light propagating between optical wavelength diplexer4303and optical assembly4023. Optical port532Ntransmits light propagating between optical wavelength diplexer430Nand optical assembly402N.

Optical wavelength diplexer4301is an optical filter configured to: (i) pass through the optical signals corresponding to the wavelengths λ1and λN+1; and (ii) reflect at an angle the optical signals corresponding to the wavelengths λ2, λ3, . . . , λN, λN+2, λN+3, . . . , λ2N. The optical signals corresponding to the wavelengths λ1and λN+1are coupled through optical port5321to various optical components of optical assembly4021′ in a manner similar to that described in reference toFIG.4. The optical signals corresponding to the wavelengths λ2, λ3, . . . , λN, λN+2, λN+3, . . . , λ2Nare directed towards optical wavelength diplexer4302.

Optical wavelength diplexer4302is an optical filter configured to: (i) pass through the optical signals corresponding to the wavelengths λ3, . . . , λN, λN+3, . . . , λ2N; and (ii) reflect at an angle the optical signals corresponding to the wavelengths λ2and λN+2. The optical signals corresponding to the wavelengths λ2and λN+2are coupled through optical port5322to various optical components of optical assembly4022′ in a manner similar to that described in reference toFIG.4. The optical signals corresponding to the wavelengths λ3, . . . , λN, λN+3, . . . , λ2Nare directed towards optical wavelength diplexer4303.

Optical wavelength diplexer4303is an optical filter configured to: (i) pass through the optical signals corresponding to the wavelengths λ4, . . . , λN, λN+4, . . . , λ2N; and (ii) reflect at an angle the optical signals corresponding to the wavelengths λ3and λN+3. The optical signals corresponding to the wavelengths λ3and λN+3are coupled through optical port5323to various optical components of optical assembly4023in a manner similar to that described in reference toFIG.4. The optical signals corresponding to the wavelengths λ4, . . . , λN, λ+4, . . . , λ2Nare directed towards optical wavelength diplexer430Nand any intervening optical wavelength diplexers430n(if present, not explicitly shown inFIG.5), where n=4, . . . , N−1.

Optical wavelength diplexer430Nis an optical filter configured to: (i) reflect at an angle the optical signals corresponding to the wavelengths λNand λ2N; and (i) block or otherwise discard other optical signals (if present). The optical signals corresponding to the wavelengths λNand λ2Nare coupled through optical port532Nto various optical components of optical assembly402Nin a manner similar to that described in reference toFIG.4.

In one possible alternative embodiment, optical wavelength diplexer430Ncan be replaced by a mirror or other suitable light reflector.

In another possible alternative embodiment, optical wavelength diplexer430Ncan be removed, and optical assembly402Ncan be repositioned to directly optically couple to the next upstream optical wavelength diplexer430(e.g., optical wavelength diplexer430N−1, not explicitly shown inFIG.5). An example of such repositioning can be obtained by examining the relative positions of optical wavelength diplexer430and optical assembly4022shown inFIG.4.

In an example embodiment, passive optical router530performs an optical function similar to that of a multi-port optical add-drop multiplexer. More specifically, such an optical add-drop multiplexer can be designed and configured to: (i) drop optical signals corresponding to the carrier wavelengths λN+1, . . . , λ2Nat different respective optical ports thereof; and (ii) add optical signals corresponding to the carrier wavelengths λ1, . . . , λNat said different respective optical ports thereof. Based on the above description, a person of ordinary skill in the art will understand how to make and use alternative (e.g., grating-based) embodiments of passive optical router530.

In some alternative embodiments, passive optical router530may be optically coupled to more than one optical fiber290.

For example, in one alternative embodiment, another optical fiber290and another ball lens284can be placed in device500next to optical wavelength diplexer430n(where n=2, 3, . . . , N−1) in a planar arrangement similar to that of the shown optical fiber290, ball lens284, and optical wavelength diplexer4301. As a non-limiting example,FIG.5indicates, with a dashed line2903, a possible location of such another optical fiber290coupled to optical wavelength diplexer4303.

In another alternative embodiment, another optical fiber290and another ball lens284can replace one of optical assemblies4022-402Nin device500.

A person of ordinary skill in the art will understand how to change the relevant optical characteristics of some or all of the optical wavelength diplexers430in the above-indicated alternative embodiments of device500to implement various wavelength routing schemes with respect to the shown optical fiber290and said another optical fiber290.

Some wavelength plans for device500may rely on wavelength-diplexer slabs430designed for a relatively steep angle of light-beam incidence (e.g., smaller than 45 degrees with respect to the normal). In such embodiments, respective mirrors (not shown inFIG.5) may be used in conjunction with at least some of the wavelength-diplexer slabs430to realize a more compact placement of the various wavelength-diplexer slabs430and for the tight optical coupling of the corresponding optical elements in passive optical router530.

In an example embodiment, passive optical router530can be used to implement the whole or a portion of a MUX/DMUX120(also seeFIG.1).

According to an example embodiment disclosed above, e.g., in the summary section and/or in reference to any one or any combination of some or all ofFIGS.1-5, provided is an apparatus comprising: a substrate (e.g.,202,FIG.4) having a substantially planar surface (e.g.,302,FIG.3); first and second optical transceivers (e.g.,4021,4022,FIG.4) fixed to said substrate adjacent and along said planar surface, the first and second optical transceivers having non-overlapping footprints on said planar surface (e.g., as inFIG.4); and a passive optical filter (e.g.,430,FIG.4) fixed to said substrate and configured to direct along said planar surface, between an end face (e.g.,288,FIG.4) of an optical fiber (e.g.,290,FIG.4) and the first optical transceiver, light of first wavelengths (e.g., λ1, λ3,FIG.4), and to direct along said planar surface, between the end face and the second optical transceiver, light of second wavelengths (e.g., λ2, λ4,FIG.4), the first wavelengths being different from the second wavelengths.

In some embodiments of the above apparatus, the apparatus further comprises a connector (e.g.,390,FIG.3) fixed to said substrate to stabilize an end segment of the optical fiber along said planar surface, the end segment including the end face.

In some embodiments of any of the above apparatus, the apparatus further comprises one or more bulk lenses (e.g.,284,414,484,FIG.4) fixed to said substrate to direct a light beam between the end face and the first optical receiver substantially parallel to said planar surface, and to direct a light beam between the end face and the second optical receiver substantially parallel to said planar surface.

In some embodiments of any of the above apparatus, the one or more bulk lenses include an optical relay system (e.g.,414,484,FIG.4) to direct a light beam between the passive optical filter and the second optical receiver.

In some embodiments of any of the above apparatus, each of the optical transceivers includes a respective photodiode (e.g.,270,FIG.4) configured to receive light from the end face via a respective first optical path through the optical transceiver and includes a respective light source (e.g.,210,FIG.4) configured to transmit light to the end face via a respective second optical path through the optical transceiver, each of said respective first and second optical paths being substantially parallel to said planar surface.

In some embodiments of any of the above apparatus, each of the optical transceivers includes a respective slab-like optical filter (e.g.,230,FIG.4) having main surfaces thereof normal to said planar surface and optically coupling both the respective photodiode and the respective light source to the passive optical filter.

In some embodiments of any of the above apparatus, each of the optical transceivers comprises a respective coherent optical detector that includes the respective photodiode.

In some embodiments of any of the above apparatus, the passive optical filter comprises an optical slab (e.g.,430,FIG.4) fixed to said substrate and having main surfaces thereof normal to said planar surface.

In some embodiments of any of the above apparatus, the optical slab is configured to transmit therethrough light of the first wavelengths and to reflect therefrom light of the second wavelengths.

In some embodiments of any of the above apparatus, the apparatus further comprises a passive optical router (e.g.,530,FIG.5) that includes the passive optical filter, the passive optical router having a first optical port (e.g.,528,FIG.5) and three or more second optical ports (e.g.,5321-532N,FIG.5), the first optical port being configured to transmit light propagating between the passive optical router and the end face, one of the second optical ports being configured to transmit light propagating between the passive optical router and the first optical transceiver, and another one of the second optical ports being configured to transmit light propagating between the passive optical router and the second optical transceiver.

In some embodiments of any of the above apparatus, the passive optical router is fixed to said substrate adjacent and along said planar surface and has a footprint on said planar surface non-overlapping with the footprints of the first and second optical transceivers (e.g., as inFIG.5).

In some embodiments of any of the above apparatus, the passive optical router comprises a sequence of optical slabs (e.g.,4301-430N,FIG.5) optically coupled to one another and to the end face, each of the slabs having main surfaces thereof normal to said planar surface.

In some embodiments of any of the above apparatus, the apparatus further comprises one or more additional optical transceivers (e.g.,4023-402N,FIG.5) fixed to said substrate adjacent and along said planar surface, each of said one or more additional optical transceivers having a footprint on said planar surface that does not overlap with the footprints of other optical transceivers thereon (e.g., as inFIG.5); and wherein the passive optical router is configured to direct light between the end face and each one of the first, second, and additional optical transceivers through a respective one of the second optical ports.

In some embodiments of any of the above apparatus, the passive optical router is a part of an optical add-drop multiplexer.

In some embodiments of any of the above apparatus, different ones of the second optical ports are configured to transmit light of different respective non-overlapping sets of wavelengths.

In some embodiments of any of the above apparatus, each of the first and second optical ports is a bidirectional optical port.

In some embodiments of any of the above apparatus, the passive optical router is configured to receive light from or transmit light to an end face of another optical fiber (e.g.,2903,FIG.5) along said planar surface.

While this disclosure includes references to illustrative embodiments, this specification is not intended to be construed in a limiting sense.

For example, while various embodiments are described above as being constructed using ball lenses, other suitable lenses and/or lens systems may also be used in at least some alternative embodiments.

Various modifications of the described embodiments, as well as other embodiments within the scope of the disclosure, which are apparent to persons skilled in the art to which the disclosure pertains are deemed to lie within the principle and scope of the disclosure, e.g., as expressed in the following claims.

It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this disclosure may be made by those skilled in the art without departing from the scope of the disclosure, e.g., as expressed in the following claims.

Unless otherwise specified herein, the use of the ordinal adjectives “first,” “second,” “third,” etc., to refer to an object of a plurality of like objects merely indicates that different instances of such like objects are being referred to, and is not intended to imply that the like objects so referred-to have to be in a corresponding order or sequence, either temporally, spatially, in ranking, or in any other manner.

Throughout the detailed description, the drawings, which are not to scale, are illustrative only and are used in order to explain, rather than limit the disclosure. The use of terms such as height, length, width, top, bottom, is strictly to facilitate the description of the embodiments and is not intended to limit the embodiments to a specific orientation. For example, height does not imply only a vertical rise limitation, but is used to identify one of the three dimensions of a three dimensional structure as shown in the figures. Such “height” would be vertical where the corresponding substrate is horizontal but would be horizontal where the corresponding substrate is vertical, and so on.

Also for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. The same type of distinction applies to the use of terms “attached” and “directly attached,” as applied to a description of a physical structure. For example, a relatively thin layer of adhesive or other suitable binder can be used to implement such “direct attachment” of the two corresponding components in such physical structure.

It should be appreciated by those of ordinary skill in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the disclosure.